bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mechanism Responsible for a Low Electrostatic Discharge Failure Threshold of an Output Buffer Circuit with Low Current Drive Capability
Authors: Liao Jiaw-Ren Shih , Yue Boon-Khim Liew
Published: October 2002

The electrostatic discharge (ESD) failure threshold of an output
buffer is observed to be sensitive to the used-gate finger number. It
is found that the lower the current drive capability, the lower the
ESD failure threshold, and the damage sites of the output buffer are
always located at the used gate n-channel metal-oxide semiconductor
(NMOS) transistors. This observation can only be explained on the
basis of the energy dissipation (E=V
SP×I
D×time)
in each finger, where I
D is composed
of channel current and bipolar current. From the real-time
current-voltage measurement during ESD zapping, three phenomena are
observed. The first is that a transistor with a floating gate
(used-gate fingers) has a larger snapback voltage (V
SP)
than that with a grounded gate transistor. The second is that due to
the accumulation of hot holes in the floating gate, a constant gate
voltage can be induced during the ESD zapping. The last is that this
induced-gate-voltage can assist the switching on of the NMOS
transistors and reduction of the ESD duration. Therefore, the ESD
duration of a transistor with high current drive capability will be
much shorter than that of low current drive capability. As a result,
high current drive capability leads to a high ESD failure threshold.
Measurement of Young's Modulus of Silicon Single Crystal at High Temperature and Its Dependency on Boron Concentration Using the Flexural Vibration Method
Authors: Ono Naoki , Kitamura Kounosuke , Nakajima Ken , Shimanuki Yasushi
Published: October 2002

Young's moduli of silicon single crystals were measured in the temperature
range from room temperature to 1000°C. The moduli were calculated from the
resonance frequencies in the flexural mode of vibration. This method for measuring the
moduli is thought to be more reliable than using the conventional tensile tests. Young's
modulus in the temperature range from 800°C to 1000°C did not
decrease as much as expected. The dependency on boron concentration was also investigated
and found to be minimal in this temperature range and at boron concentrations of up to
8.5×1018 atoms/cm3.
Optical Measurement of Resonant Oscillation and Marangoni Convection-Induced Oscillation in a Molten Silicon Surface
Authors: Sumiji Masanobu , Nakamura Shin , Onuma Kazuo , Hibiya Taketoshi
Published: October 2002

Surface oscillation due to oscillatory Marangoni flow in a
liquid bridge of molten silicon was observed through
interferometry. To obtain higher resolution, interferograms taken
from a molten silicon surface and a reference sample were converted
to phase-distribution profiles by using spatial
phase-measurement. We analyzed the phase-distribution profiles by
measuring the radial displacement, azimuthal phase value gradient,
and axial phase value gradient. The total radial displacement was
about 1.5 µm over a 2.0-s period. The radial displacement and
axial phase value gradient showed in-phase correlation, which
suggests a traveling wave in the azimuthal direction. The Fourier
spectrum of the radial displacement showed several peaks from 0.5 to
5 Hz. These frequencies corresponded to the frequencies of
Marangoni flow reported based on other methods. The spectrum also
showed two single peaks at 21 and 24.5 Hz. These frequencies agreed
well with theoretical resonant frequencies of the liquid bridge.
Dynamic Scanning Force Microscopy at Low Temperatures
Authors: Allers Wolf , Schwarz Alexander , Hölscher Hendrik , Schwarz Udo Dietmar , Wiesendanger Roland
Published: October 2002

In this paper, we review the design and various applications of a low temperature scanning force microscope for ultrahigh vacuum. It has been adopted for dynamic mode measurements, a powerful method to image surfaces with a resolution similar to scanning tunneling microscopy, but without the limitation to conducting materials. With this instrument, we have studied semiconducting (InAs), conducting (HOPG) and insulating samples (xenon thin film). Finally, we discuss a new experimental method to determine the tip-sample interaction with high accuracy.
Three-Dimensional Simulation of Silicon Melt Flow in Electromagnetic Czochralski Crystal Growth
Authors: Wei Wang Wei Wang , Masahito Watanabe Masahito Watanabe , Taketoshi Hibiya Taketoshi Hibiya , Takahiko Tanahashi Takahiko Tanahashi
Published: October 2002

The three-dimensional silicon melt flow in Electromagnetic Czochralski (EMCZ) growth without crucible rotation was numerically investigated using the finite element method. Due to the interaction of an axial magnetic with a constant electric current passing through the melt from the growing crystal to an electrode attached to the melt surface, an electromagnetic force (EMF) was generated. The EMF significantly suppressed the buoyant convection, and created a large axially elongated vortex in the bulk melt and a small one near the electrode. In EMCZ growth, the heat and mass transfers are thus controlled mostly through the axially elongated vortex driven by the local electromagnetic force.The feature of the melt flow is in qualitative agreement with experimental observation.
Structures of an Oxygen-Deficient TiO2(110) Surface Studied by Noncontact Atomic Force Microscopy
Authors: Ashino Makoto , Uchihashi Takayuki , Yokoyama Kousuke , Sugawara Yasuhiro , Morita Seizo , Ishikawa Mitsuru
Published: October 2002

We investigated an oxygen-deficient TiO2(110) surface using
noncontact atomic force microscopy, revealing the defect structures
of topmost oxygen atoms. We successfully observed not only
half-height steps along the [112] direction caused by
crystallographic shear planes belonging to the {132} family but
also novel half-height steps along [001]. The terrace between the
half-height steps along the [112] direction was terminated with
added Ti2O3 rows including some defect structures. We
proposed that the half-height steps along the [001] direction were
formed together with the half-height steps along the [112]
direction.
Protein Stretching IV: Analysis of Force-Extension Curves
Authors: Atsushi Ikai Atsushi Ikai , Tong Wang Tong Wang
Published: October 2002

Force curve measurement by atomic force microscopy has
begun to establish its usefulness as a new tool for the
investigation of the physical properties of biological materials and
processes. Since directly observable quantity in such experiments
is the magnitude of the deflection of the cantilever in response to the
force exerted on it, it is often difficult to distinguish specific
sample responses that are to be measured from superfluous ones due to
unwanted interactions between the atomic force microscope (AFM) tip and the sample, or the
substrate. In this study, we analyzed force curves obtained in our
laboratory over protein samples and tried to extract vital information
on the mechanical strength of proteins under different conditions.
Investigation of Nonswitching Regions in Ferroelectric Thin Films Using Scanning Force Microscopy
Authors: Saya Yuko , Watanabe Shunji , Kawai Maki , Yamada Hirofumi , Matsushige Kazumi
Published: October 2002

Nonswitching regions which degrade the electrical properties of
ferroelectric thin films were investigated by scanning probe
microscopy. An 80-nm-thick PbZr0.5Ti0.5O3(001)(PZT)
ferroelectric thin film and a YBa2Cu3O7-δ(100)
bottom electrode were grown on
SrTiO3(100) substrates by the pulsed laser deposition method. We
successfully detected nonswitching regions in the PZT thin films by
measuring ferroelectric hysteresis loops using a scanning probe
microscope, and the hysteresis loops showed an asymmetric shift
toward negative remanent polarization. It is suggested that the
nonswitching regions originate from dislocations caused by a lattice
mismatch between the PbZr0.5Ti0.5O3(001) and the
YBa2Cu3O7-δ(100). The effective thickness of the nonswitching regions is estimated to be 20 nm from the amount of the shift of the hysteresis loops.
Heat Treatment with High-Pressure H2O Vapor of Pulsed Laser Crystallized Silicon Films
Authors: Katsumi Asada Katsumi Asada , Keiji Sakamoto Keiji Sakamoto , Tadashi Watanabe Tadashi Watanabe , Toshiyuki Sameshima Toshiyuki Sameshima , Seiichiro Higashi Seiichiro Higashi
Published: October 2002

Improvement of electrical properties for 7.4 ×1017 cm-3 phosphorus-doped pulsed laser crystallized silicon films of 50 nm thickness formed on quartz glass substrates was achieved by heat treatment with high-pressure H2O vapor. The electrical conductivity was increased from 1.3 ×10-5 S/cm (as-crystallized) to 2 S/cm by annealing at 270°C for 3 h with 1.3 ×106 Pa H2O vapor. The spin density of undoped laser crystallized silicon films was reduced from 1.6 ×1018 cm-3 (as-crystallized) to 1.2 ×1017 cm-3 by annealing at 310°C for 3 h with 1.3 ×106 Pa H2O vapor. Theoretical analysis revealed that the potential barrier height at grain boundaries decreased from 0.3 eV (as-crystallized) to 0.002 eV. High-pressure H2O vapor annealing offer the possibility of reducing the density of defects states through oxidation of the defects at low temperature.
A Comparison of Behaviors between Hydrogenated/Unhydrogenated Polysilicon Thin Film Transistors under Electric Stress
Authors: Yaung Dun-Nian , Fang Yean-Kuen , Lee Kan-Yuan , Hwang Kuo-Ching , Wuu Shou-Gwo , Liang Mong-Song
Published: October 2002

The effects and kinetics of electric stress on
hydrogenated/unhydrogenated polysilicon thin-film transistors
(poly-TFTs) have been investigated. The poststress characteristics
of TFTs depend not only on the stress condition but also on the
hydrogenation process. Under off-state stress conditions
(V
gs=0 V and V
ds=-15 V), the poststress
subthreshold swing and on-current of unhydrogenated TFTs are
improved due to the annealing effect of donor-like traps, which is
caused by tunneling electrons/captured holes interaction. While
under on-state stress conditions (V
gs=-20 V and
V
ds=-15 V), these characteristics are first improved,
then deteriorated because of electron trapping in the gate oxide and
carrier-induced metastable defects in the channel. The poststress
characteristics will not be improved if the trap states have been
previously removed by hydrogenation. In addition, we found that the
poststress characteristics under off-state stress conditions are not
changed after thermal annealing at 250°C for 30 min, while the
metastable defects and electron trapping under on-state stress
conditions can be easily annealed after thermal treatment.
Performance of GaN-Based Semiconductor Laser with Spectral Broadening due to Compositional Inhomogeneity in GaInN Active Layer
Authors: Kamiyama Satoshi , Iwaya Motoaki , Amano Hiroshi , Akasaki Isamu
Published: October 2002

We have quantitatively analyzed the effect of spectral broadening due to a compositional
inhomogeneity in GaInN active layer, on the threshold current density of GaN-based
semiconductor lasers, using a simple broadening function model. Since the compositional
inhomogeneity in the GaInN active layer directly results in the spectral broadening, we treated
a broadening factor as a parameter showing the amount of inhomogeneity. We have shown a
relationship between the threshold current density of GaN-based semiconductor lasers and
full-width at half maximum (FWHM) of spontaneous emission spectra from the GaInN active
layer of the devices, which is a useful information for realizing high performance GaN-based
semiconductor lasers.
Stoichiometry Study of S-Terminated GaAs(001)-(2 ×6) Surface with Synchrotron Radiation Photoelectron Spectroscopy
Authors: Masahiko Shimoda Masahiko Shimoda , Shiro Tsukamoto Shiro Tsukamoto , Takahisa Ohno Takahisa Ohno , Nobuyuki Koguchi Nobuyuki Koguchi , Munehiro Sugiyama Munehiro Sugiyama , Satoshi Maeyama Satoshi Maeyama , Yoshio Watanabe Yoshio Watanabe
Published: October 2002

Synchrotron radiation photoelectron spectroscopy (SRPES) has been performed to investigate the surface stoichiometry of the S-terminated GaAs(001)-(2 ×6), and in particular, to determine the chemical species of the five dimers, which are separated by missing dimers and form the unit structure of the (2 ×6) reconstruction. The S 2p photoemission spectra show a significant decrease in the peak intensity with increasing substrate temperature, whereas no significant changes are observed for the As 3d photoemission spectra The Ga 3d spectra are decomposed into a bulk component and more than one surface component, one of which is attributed to a Ga–S bond and decreases in accordance with the change observed in the S 2p spectra. These results strongly support the model that each pair of the five dimers in the (2 ×6) reconstruction consists of S–S dimers.
Effects of Wet Chemistry Pre-gate Clean Strategies on the Organic Contamination of Gate Oxides for Metal-Oxide-Semiconductor Field Effect Transistor
Authors: Guan Jay J. , Gale Glenn W. , Bennett Joe
Published: October 2002

It is known that organic contamination can seriously degrade the electrical
performance of gate oxides for metal-oxide-semiconductor field effect
transistor (MOSFET) applications. In this paper, organic contamination of wafer
surfaces cleaned by different pre-gate clean conditions and subsequently exposed to
cleanroom ambience was investigated using time-of-flight secondary ion mass
spectroscopy (TOF-SIMS), and the carbon level from thermally decomposed organic
species directly trapped in the gate oxides after thermal oxidation and polysilicon
deposition was probed using secondary ion mass spectroscopy (SIMS) depth profiling.
The C concentration in the oxide-polysilicon gate stack obtained from SIMS depth
profiling closely correlates with the total TOF-SIMS peak intensity of organic
contaminants detected on post clean wafer surfaces. A quantified carbon concentration
on the order of 1012 atoms/cm2 was obtained at the interfaces using SIMS
depth profiling calibrated with an implanted C standard. It was found that the
susceptibility of wafer surfaces to organic contamination that eventually affects the
level of oxide-polysilicon interfacial carbon appears to be highly dependent on the
surface termination.
Polarization Switching and Dielectric Relaxations in Ferroelectric Liquid Crystals
Authors: Ahuja Jasjit K. , Raina K. K.
Published: October 2002

Polarization switching and dielectric relaxations have been investigated in two novel ferroelectric liquid crystal mixtures. The samples of helical pitch ∼12 µm and 0.43 µm respectively were sandwiched in planar cells of 5 µm thickness. P
S, τr and γ have been evaluated using polarization reversal current technique. Dielectric relaxation modes have been studied under different bias conditions. In volume stabilized cell configuration (p
0 ≪d) bulk domain mode appears due to the formation of modulated domain structures in bulk region while in surface stabilized cell configuration (p
0 ≫d) surface stabilized domain mode was observed. New relaxation mode appeared at all bias fields in SmC* phase due to the surface effects.
Melting and Solidification Behaviour of Lead Nanoparticles Embedded in Amorphous and Quasicrystalline Matrices of Al–Cu–V
Authors: Singh Alok , Tsai A. P.
Published: October 2002

Melting and solidification behaviour of lead particles of size about 30 nm has been studied in amorphous and quasicrystalline matrices of an Al75Cu15V10alloy. The lead particles had semi-shperical morphology, and often showed twinning. The particles showed a depression in the melting temperature by about 17°C in the amorphous matrix and about 6°C in the quasicrystalline matrix, as compared to the bulk melting temperature. On solidification an undercooling of greater than 60°C is obtained. The lowering of the melting temperature and a high undercooling on solidification is qualitatively explained to be due to the interfacial energies of the liquid or solid lead with the matrix.
Hardness and Structure of a-CNx Films Synthesized by Chemical Vapor Deposition
Authors: Daisuke Tanaka Daisuke Tanaka , Yoshiaki Ohkawara Yoshiaki Ohkawara , Noriko Itoh Noriko Itoh , Shigeo Ohshio Shigeo Ohshio , Haruhiko Ito Haruhiko Ito , Hidetoshi Saitoh Hidetoshi Saitoh
Published: October 2002

Mechanically hard a-CN
x
films were synthesized using a combination of ion bombardment and the chemical vapor deposition process using the dissociative excitation reaction of BrCN with Ar metastable atoms. Nanoindentation tests disclosed that the indentation hardness, Young's modulus and elastic recovery increased with increasing ion-accelerating voltage. Moreover, the degree of flow among clusters decreased in the ion-bombarded sample. The D (disordered)-band absorption on an infrared absorption spectrum was replaced by a C–N absorption assigned to the tertiary aromatic amine. These results suggest that the internal and external structures of the carbon nitride cluster change from the two-dimensional order to the three-dimensional order of C–N. The structure of hard a-CN
x
is clearly distinguishable from nitrogen-containing diamond-like carbon.
Resonance Ionization Diode-Laser Spectroscopy of Neutral Atomic Beam Produced by Pulsed-Ablation Charge Exchange
Authors: Mitsuto Isobe Mitsuto Isobe , Tatsuya Minowa Tatsuya Minowa , Wei-Guo Jin Wei-Guo Jin , Hidetsugu Katsuragawa Hidetsugu Katsuragawa , Haruko Uematsu Haruko Uematsu
Published: October 2002

The lithium ion beam was neutralized in a newly developed charge-exchange cell. The charge exchange was performed with sodium, lithium and iron vapors. The lithium atom was photoionized in a three-step resonance-ionization scheme where the first-step excitation was performed with a cw external-cavity diode laser. The resonance ionization with a diode laser and a pulsed dye laser was as efficient as that with two high-power pulsed dye lasers.
Deuterization and Deuterium Reactions in the Electrolyses of D2O with the Double Structure Cathode and the Bulk Cathode
Authors: Arata Yoshiaki , Zhang Yue-Chang
Published: October 2002

The deuterium concentration in the bulk Pd metal used as a cathode in the electrolysis of D2O is found to be much less than that in fine Pd powders of the nano-scale in a double-structure (DS) cathode. In marked contrast to the case with the DS cathode, neither excess heat nor 4He production are observed with the bulk Pd cathode.
A Thermal Analysis of a Magneto-Optical Recording Mechanism with the Magnetic Field Modulation Method on a Land and Groove Substrate
Authors: Nakaoki Ariyoshi , Kaneko Masahiko
Published: October 2002

The power tolerance in recording is one of the most significant issues in the case of rewritable optical disk systems. Magneto-optical land/groove recording has been investigated by magnetic field modulation with pulse irradiation. The lower limit and the upper limit of the power tolerance are determined from the overwriting and the crosswrite characteristics, respectively. The experimental dependence of the power tolerance on track pitch, pulse duty, and optical spot size has been in good agreement with our model based on the thermal analysis. According to our model, the mark width is exactly the width of a recording track for the lower limit of power tolerance, and it spreads into the neighboring track for the upper limit. The deep groove substrate has been found experimentally and theoretically to be effective for improving the power tolerance.
Additive Dose Single and Multiple Aliquot Methods of Equivalent Dose Determination Compared for Quartz Luminescence Stimulated by Green Light
Authors: Hong Duk-Geun , Galloway Robert , Hashimoto Tetsuo
Published: October 2002

For quartz stimulated by green light, several comparisons are presented between traditional multiple aliquot results and corrected single aliquot measurements. The dependence of the luminescence response on added dose is compared for two techniques and it is found that the closeness of similarity depends on the preheating used. For naturally dosed samples, the comparisons are made both for materials that were originally zeroed by heating and others originally bleached by exposure to light. Three alternative single aliquot correction procedures are used.
Hybrid Cryogenic Refrigerator: Combination of Brayton Magnetic-Cooling and Gifford-McMahon Gas-Cooling System
Authors: Yayama Hideki , Hatta Yoshiro , Makimoto Yoshitsugu , Tomokiyo Akihisa
Published: October 2002

We propose a new cryogenic refrigerator which is a hybrid of the Brayton magnetic-cooling cycle and the Gifford-McMahon (GM) gas-cooling cycle. We evaluate the refrigeration power of the refrigerator with ErNi regenerator material by a numerical simulation. The results show a remarkably high refrigeration power in contrast to the conventional simple GM gas-refrigerator.
Triple-Exposure Method for Fabricating Triangular-Lattice Photonic Crystals
Authors: Tokushima Masatoshi , Kosaka Hideo , Tomita Akihisa , Yamada Hirohito
Published: October 2002

We have developed a triple-exposure method for defining a triangular-lattice pattern to form two-dimensional (2D) photonic-crystal (PC) waveguides operating at a 1.55-µm wavelength. This method, in which three line-and-space (L/S) patterns are projected onto a wafer in three different directions, allows us to define a smaller-pitch triangular-lattice pattern compared to that definable by the conventional exposure method. When 0.61-µm-pitch L/S masks were employed, an i-line stepper successfully resolved a 0.7-µm-hole-pitch triangular-lattice pattern, which was at the resolution limit. A sharply bent line defect was introduced as a waveguide into the pattern by using L/S photomasks with the corresponding parts of the space areas removed. We applied this method to fabricate a triangular-lattice 2D PC with a hole pitch of 0.8 µm and a minimum feature size of 0.05 µm. The measured photonic bandgap (PBG) of this PC indicated that it operates at a near-1.55-µm wavelength.
Potential Energy Surface and Dynamics of Pd/MgO(001) System as Investigated by Periodic Density Functional Calculations and Classical Molecular Dynamics Simulations
Authors: Endou Akira , Teraishi Kazuo , Yajima Kenji , Yoshizawa Kentaro , Ohashi Nobumoto , Takami Seiichi , Kubo Momoji , Miyamoto Akira , Broclawik Ewa
Published: October 2002

This study is the first attempt to establish reliable
interatomic potential parameters for the two-body classical force
field from the interaction energies of the Pd1/MgO(001)
interface obtained by the periodic density functional (DFT)
calculations. Using these parameters, we can simulate the potential
energy surface (PES) of the Pd1/MgO(001) system and its dynamic
behavior in a shorter time, using the classical molecular dynamics
(MD) method. The fitted PES of the Pd1/MgO(001) system obtained
using the present parameters suggests the appearance of a saddle
point during the migration of the Pd adatom on the fourfold hollow
site. The dynamic behavior of the Pd adatom on the MgO(001) surface
was also simulated by the classical MD method using the present
parameters. These results agreed well with both the saddle point and
the migration path of the adatom which was previously predicted by
the Car-Parinello method.
Adsorption and Structural Energetics of Chemisorbed F Atom on Si(100)-a Density Functional Theory (DFT) Study
Authors: Chatterjee Abhijit , Iwasaki Takashi , Ebina Takeo
Published: October 2002

We report density functional electronic structure calculations related to the initial
fluorination of the Si(100)-2×1 surface. Embedded finite silicon clusters are used
to model an extended Si(100)-2×1 surface. Two high symmetry pathways and subsequent
adsorption sites were examined: (i) adsorption of an fluorine atom directing onto a silicon
dangling bond to form a monocoordinated fluorine atom (ii) adsorption of a fluorine atom
directing on top of silicon dimer to form a bridging dicoordinated fluorine atom. However,
in the later case we find that no barrier exists for the bridging fluorine atom to slide
towards silicon dimer dangling bond to form more stable mono coordinated Si–F bond. We
calculated activation barriers and equilibrium surface configuration as a function of
fluorine coverage upto 2.0 ML. We report the harmonic vibrational frequency for surface
fluorosilyl species. We compared the stability of the fluorinated surface. We finally
propose a plausible mechanism of the initial stage of fluorine etching.
First-Principles Study of the Surface Electronic Structures of Transition Metal Carbides
Authors: Kobayashi Kazuaki
Published: October 2002

Surfaces of transition metal carbides (TiC, ZrC, NbC, HfC and
TaC(001)-1×1) are investigated using the first-principles
molecular dynamics (FPMD) method.
By the full structural optimization of the surface, the carbon and
transition metal atoms on the top layer move outward and inward,
respectively.
All the calculated electronic states of surfaces are metallic.
A non-linear core correction is considered for pseudopotentials of
transition metals and plays an important role in the structural
optimization.
Spatial and Spectroscopic Profiles of the Kondo Resonance for a Single Magnetic Atom on a Metal Surface under an External Magnetic Field
Authors: Diño Wilson Agerico , Imoto Kunihiro , Kasai Hideaki , Okiji Ayao
Published: October 2002

Manifestations of the Kondo effect on an atomic length scale on and around a magnetic atom adsorbed on a nonmagnetic metal surface differ depending on which spectroscopic mode the scanning tunneling microscope is operated. In a series of reports, we showed that the Kondo effect can be directly observed as protrusions (peaks) in the spatial distribution of the tunneling current, and that the protrusions (peaks) observed in the spatial distribution of the tunneling current correspond to the resonances observed in the differential conductance spectra. In this report, we show that upon applying an external magnetic field with increasing magnitude, the protrusions (peaks) observed in the spin-resolved spatial distribution of the tunneling current would decrease monotonically for spin-down electrons, but change non-monotonically for spin-up electrons. We also show that, upon applying an external magnetic field, additional features about the Fermi level appear for the narrow dip structure observed for the corresponding differential conductance spectra.
Ultrathin Organic Layers on Silicon Surfaces
Authors: Hamers Robert J. , Hovis Jennifer S. , Coulter Sarah K. , Ellison Mark D. , Padowitz David F.
Published: October 2002

Ultrathin organic layers of organic molecules can be produced on the Silicon(001) surface using surface analogs of well-known cycloaddition reactions from organic chemistry. Molecules containing one or more unsaturated C=C can readily bond to the surface at room temperature. Since these reactions form two bonds between the molecule and the surface, the attached molecules are also oriented. More complex molecules containing conjugated pi-electron systems such as styrene can also be bonded to the surface with high selectivity for specific bonds. This manuscript reviews recent progress in forming ultrathin organic layers on silicon, and the current understand of the relevant reaction mechanisms.
Surface Morphology of Growing Al on Si(111)7×7 and Si(111)√3×√3–Al Substrates by Reflection High-Energy Electron Diffraction
Authors: Yoshimi Horio Yoshimi Horio
Published: October 2002

Morphology of thin Al films grown on Si(111)7×7 and Si(111)√3×√3–Al substrates was investigated by glancing angle dependent reflection high-energy electron diffraction (RHEED). Comparing the experimental RHEED patterns with the calculated ones based on the refraction effect and Laue function at each glancing angle, the averaged slope angle of the deposited Al islands and the averaged domain size are estimated for both the systems. The morphological differences between the two systems are quantitatively clarified.
Surface Morphology Development during Molecular Beam Epitaxy Growth on a GaAs(100) Vicinal Surface
Authors: Takaaki Kawamura Takaaki Kawamura , Junko Maruta Junko Maruta , Akira Ishii Akira Ishii
Published: October 2002

Using a kinetic Monte Carlo simulation, the homoepitaxial growth on a GaAs(100) vicinal surface misoriented toward the [011] direction has been studied. The growth mode transition, the topmost coverage variation and the surface
morphology development are examined by varying the As/Ga flux ratio as well as the temperature. The kinetics of As play an important role in determining the growth mode transition, the coverage variation and the surface morphology during growth, which are similar to the case of a vicinal surface misoriented toward the [011] direction. A continuous growth mode transition is observed and is related to the surface morphology.
Hydrogen as the Cause of Step Bunching Formed on Vicinal GaAs(001)
Authors: Hata Kenji , Shigekawa Hidemi , Ueda Takashi , Akiyama Masahiro , Okano Tatsuo
Published: October 2002

In order to elucidate the cause of step bunching formed on
vicinal GaAs(001) annealed in AsH3/H2 ambient, we
investigated the surface of vicinal GaAs(001) annealed in H2,
AsH3/N2, AsH3/H2, and N2 by scanning
tunneling microscope. Since step bunches always formed on surfaces
annealed with hydrogen but not on surfaces annealed in ambients
without hydrogen, we conclude that hydrogen is crucial in the
formation of step bunching.
Scanning Tunneling Microscopy Observation of the Formation of the Smallest Dimer–Adatom–Stacking-fault Domain on a Quenched Si(111) Surface
Authors: Shimada Wataru , Tochihara Hiroshi , Sato Tomoshige , Iwatsuki Masashi
Published: October 2002

We have observed the formation of the Dimer–Adatom–Stacking-fault (DAS)
domain in unreconstructed regions on quenched Si(111) surfaces by scanning tunneling
microscopy at 370–380°C. It is observed that a single faulted (F)-half of the
unit cell of the DAS structure is created from a corner hole of existing odd-sized
F-halves at the edge of the DAS domain. It is demonstrated that the formation of
the F-half in the domain growth follows the sequential size-change (SSC) model,
which was proposed earlier as the formation mechanism of single isolated F-halves.
The smallest DAS domain consists of three F-halves of the same size, arranged as
a triangle. We have summarized the characteristic steps of the formation towards
the smallest domain under the SSC model.
Observation of Incomplete Surface Melting of Si Using Medium-Energy Ion Scattering Spectroscopy
Authors: Sumitomo Koji , Hibino Hiroki , Homma Yoshikazu , Ogino Toshio
Published: October 2002

The disordering of Si(111) and Si(001) surfaces at high
temperatures was investigated using medium-energy ion scattering
(MEIS). We clearly observed an increase of MEIS scattering yield on
channeling geometry at 1470 K for (111) surface and at 1520 K for
(001) surface. These results support the formation of a liquid-like
layer at the transition. We also found that there is a distinct
difference in the mode of disordering on Si(111) and Si(001)
surfaces. The number of disordered atoms increases suddenly at the
transition and remains constant above the transition on Si(111)
surface. This picture of the disordering is quite similar to the
incomplete surface melting of Ge(111) surface. On the other hand,
the thickness of disordered layer on Si(001) surface continuously
increases with temperature.
Molecular Dynamics Simulations of Adhesional Forces via Hydrocarbon Films
Authors: Tamura Hiroyuki , Hui Zhou , Inaba Yusaku , Suzuki Ken , Takami Seiichi , Kubo Momoji , Miyamoto Akira
Published: October 2002

Molecular dynamics simulations have been performed to investigate the adhesional forces acting on solid surfaces due to confined hydrocarbon molecules. The pull-off forces of the n-hexane monolayer are found to be larger than those of iso-hexane. The branched methyl group of iso-hexane decreases the pull-off forces, since it decreases the stability at the equilibrium geometry.
Observation of Si(110) Surfaces by High-Temperature Scanning Tunneling Microscopy
Authors: Yoshimura Masamichi , An Toshu , Ueda Kazuyuki
Published: October 2002

The dynamic behavior of Si(110) surface structures at the phase transition temperature has been invesitgated by high-temperature scanning tunneling microscopy (STM). The faceted structures with a (17,15,1) vicinal plane are observed to remain above the phase transition temperature. The STM images reveal that the transition proceeds in units of a pair of up and down terraces at the domain boundary between the “16×2” and 1×1 phases, and that the up-and-down arrangement is found to be an energetically favorable configuration. In addition, rotated double pentagon pairs are observed to hop between the adjacent upper terraces, presumably related to the mass transport of Si across the terraces.
Indium Reevaporation during Molecular Beam Epitaxial Growth of InGaAs Layers on GaAs Substrates
Authors: Mashita Masao , Hiyama Yoshihito , Arai Kenta , Koo Bon-Heun , Yao Takafumi
Published: October 2002

We have studied the In reevaporation behavior during InGaAs growth by molecular beam epitaxy (MBE) on GaAs substrates along with lattice-matched InGaAs on InP substrates for comparison. A proposed rate-equation model for surface processes has proved that the In surface segregation effects due to the In-Ga replacement on the activation energy of In desorption are negligible. The growth temperature was changed from 540°C to 680°C. The growth rates R
InGaAs for InGaAs and R
GaAs for GaAs were determined by measuring the intensity oscillation of reflection high-energy electron diffraction (RHEED) beam. The activation energy of In reevaporation decreases with the strain in InGaAs/GaAs. The In incorporation fraction decreases with the strain in InGaAs. The In incorporation fractions of unstrained InGaAs/InP systems are larger than those of strained InGaAs/GaAs systems. The compressive stress in InGaAs shows stronger influence on decreasing In incorporation as compared to tensile stress.
Computational Chemistry Study on Initial Stages of Nitridation of Silicon Surfaces
Authors: Seiichi Takami Seiichi Takami , Hui Zhou Hui Zhou , Hiroyuki Tamura Hiroyuki Tamura , Momoji Kubo Momoji Kubo , Akira Miyamoto Akira Miyamoto
Published: October 2002

We performed computational studies on the change in enthalpy during incorporation of one nitrogen atom into bare silicon surfaces, and proposed six possible nitrided structures for the Si(100) surface and five for Si(111). The results indicated that the topmost silicon atoms on Si(111) surfaces were favorably nitrided as compared with the inner silicon atoms while both the topmost and the second layer of Si(100) were nitrided. To account for this tendency, the changes in enthalpy during nitridation were divided into the energy of deformation of the Si lattice (ΔE
def) and the energy of bond formation (ΔE
bond) between N and Si atoms. The heat of bond formation during nitridation on Si(111) was almost independent of nitridation sites. Therefore, differences in the enthalpy of nitridation between the outer surface and inner atoms resulted from ΔE
def. No distinct relationship was observed between the two energies, ΔE
def and ΔE
bond for Si(100).
X-Ray Photoelectron Spectroscopy and Temperature-Programmed Desorption Studies of Nitrided Molybdena-Alumina Catalyst
Authors: Hada Kenichiro , Nagai Masatoshi , Omi Shinzo
Published: October 2002

The relationship between the Mo oxidation states measured by X-ray photoelectron spectroscopy (XPS) and the NHXspecies was discussed based on results of temperature-programmed desorption (TPD). From the XPS analysis, the major Mo oxidation states were found to be Mo3+and Mo4+for 1.0–18.7 wt% Mo/Al2O3nitrided at 973 K. The TPD results indicated that the desorption of nitrogen and hydrogen from the nitrided Mo/Al2O3were deconvoluted to those of NHX{αN(NHX,X=0), βNand γN(NHX,X=0.6 to 1.5)} adsorbed on molybdenum species. The nitrogen species (NHX,X=0) adsorb only on Mo3+ions of the 973 K-nitrided Mo/Al2O3, but NHXspecies (X=0.6–1.5) adsorb on either Mo3+or Mo4+ions.
Surfaces and Interfaces of (Al, Ga) As Heterostructures on Unpatterned and Patterned GaAs Substrates
Authors: Jahn Uwe , Nötzel Richard , Hey Rudolf , Grahn Holger T. , Ploog Klaus H.
Published: October 2002

The correlation between surface morphology and interface properties of (Al, Ga)As quantum wells (Qwell) grown by molecular-beam epitaxy on GaAs (100) and patterned GaAs (311)Ga substrates is investigated by atomic force and scanning electron microscopy in comparison with spectrally and spatially resolved cathodoluminescence (CL), as well as micro-photoluminescence spectroscopy. On unpatterned GaAs (100) substrates, both the surfaces and Qwell interfaces exhibit at least two roughness components with correlation length on a nanometer and micrometer scale. On GaAs (311)Ga substrates patterned with mesastripes along the [011] direction, one side of the mesastripe develops a fast-growing, convex sidewall with thicker Qwell regions below, which are suitable to act as quantum wires. For a zigzag-shaped mesastripe, the growth results in wire branches with dotlike regions between them. The latter are electronically coupled with the wire branches.
Orientation Behavior of REBa2Cu3O7-y (RE = Rare Earth and Y) Films Prepared by Chemical Solution Deposition
Authors: Yamagiwa Katsuya , Hirabayashi Izumi
Published: October 2002

We have succeeded in preparing REBa2Cu3O7-y

(RE123; RE = rare-earth elements and Y)
films by chemical solution deposition (CSD) processing using metal
naphthenates under low
oxygen partial pressure. Few reports have been published on the
preparation of RE123 by
CSD processing, therefore, we prepared various RE123 films on
different substrates
systematically and examined the difference in the appearance of
a/b-axis oriented grains and
their in-plane alignment for each RE123 film as a function of
heat-treatment parameters.
Processing temperature and substrate dependencies of these films,
grown by solid phase
epitaxy, were observed to be the same as in the case of vapor phase
epitaxy. Dependencies on
ionic radius of RE elements are also observed and it is explained by
lattice misfit.
Molybdenum Carbide Prepared by Chemical Vapor Deposition
Authors: Nagai Masatoshi , Shishikura Isao , Omi Shinzo
Published: October 2002

Molybdenum carbide was synthesized on a quartz plate using a hot-wall chemical vapor deposition reactor, in a stream of MoCl5, benzene, hydrogen and argon at temperatures from 1000 to 1050 K and a total pressure of 230 Pa. The molybdenum carbides were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy. β-Mo2C was formed predominantly on the quartz plate at 1000 K and the molybdenum metal (110) phase was observed along with β-Mo2C at 1050 K. The thickness of molybdenum carbides increased in the temperature range from 1000 to 1050 K but the atomic ratio, C 1s (carbidic carbon) to Mo 3d of molybdenum carbides, gradually decreased.
Epitaxy, Modification of Electronic Structures, Overlayer-Substrate Reaction and Segregation in Ferromagnetic Co Films on Se-Treated GaAs(001) Surface
Authors: Nath Krishna G. , Maeda Fumihiko , Suzuki Satoru , Watanabe Yoshio
Published: October 2002

The electronic structure and chemical states of the overlayer and substrate in epitaxially grown Co films on Se-treated GaAs(001) 2×1 are investigated by photoemission spectroscopy (PES) using synchrotron radiation. Adatom (Co)-substrate (Ga) intermixing is found at the initial stages of Co deposition. The intermixed layer is then buried and epitaxial growth is achieved following further deposition. During the intermixing, Se is floated over the surface of Co overlayers. A small amount of As-segregation is also observed in the thicker Co films.
Resistive Barkhausen Noise at Room Temperature in Thin Ferromagnetic Wires
Authors: Yoshihiro Shimazu Yoshihiro Shimazu , Takako Noda Takako Noda , Toshio Uchikawa Toshio Uchikawa , Ken-ichi Sakai Ken-ichi Sakai
Published: October 2002

We studied the magnetoresistance of Ni wires of micron-range diameter with diameter fluctuations prepared with a simple electrochemical method. The transverse magnetoresistance at room temperature showed abrupt jumps, which strongly depended on the angle of the magnetic field with respect to the wire. We consider that these jumps are resistive Barkhausen noise due to the motion of domain walls. The artificially introduced diameter fluctuations in the sample wires, associated with the fluctuations of coercivity along the sample, were essential for the Barkhausen noise to appear. The mechanisms of pinning a domain wall in our samples and a possible novel engineering application of the Barkhausen noise are discussed.
Improvement of Optical Properties of Multilayer Quantum Dots Self-Formed in GaP/InP Short-Period Superlattices on GaAs(311)A
Authors: Watanabe Daisuke , Asahi Hajime , Noh Joo-Hyong , Fudeta Mayuko , Mori Jun , Matsuda Satoru , Asami Kumiko , Gonda Shun-ichi
Published: October 2002

Multilayer quantum dots (MQDs) structures are fabricated on a
GaAs(311)A substrate by sandwiching the quantum dots (QDs)
self-formed in (GaP)1.5(InP)1.88 short-period superlattices (SLs)
with InGaP/InAlP SL layers instead of InGaP layers, as barrier and
cladding layers. Narrower photoluminescence (PL) and
electroluminescence (EL) linewidths and weaker temperature
variations are observed for the modified MQDs compared with the
previously reported best values for MQDs with InGaP barrier and
cladding layers. PL and EL peak energies for the modified MQDs are
higher than those for the previous MQDs. These results suggest the
enhancement of carrier confinement by the use of InGaP/InAlP SL
layers as barrier and cladding layers. The temperature dependence of
EL intensity is also improved.
Formation and Shape of InAs Nanoparticles on GaAs Surfaces: Fundamental Thermodynamics
Authors: Bottomley David J.
Published: October 2002

Consideration of the heteroepitaxial growth of InAs on GaAs surfaces, and the substrate orientation-dependent growth mode, has led us to examine the thermodynamic aspects of heteroepitaxy in general. We argue that the molar Gibbs free energy G is the appropriate state function for heteroepitaxy, in contrast to Gibbs's approach of using the Helmholtz free energy, since G alone guarrantees mathematical continuity in the theory's predictions in the limit of isotropic stress. An expression for the critical heteroepitaxial strain required to melt a film is given. We comment that evidence of stress-induced surface liquid-like phenomena has been present in experiments for over 30 years, but such liquid phase phenomena had no theoretical basis until the present work. In situ electron microscopy and electron diffraction studies of heteroepitaxial growth are probably the most favourable techniques for investigating the proposed liquid phase.
Two-Gate Transistor for the Study of Si/SiO2 Interface in Silicon-on-Insulator Nano-Channel and Nanocrystalline Si Memory Device
Authors: Hinds Bruce J. , Nishiguchi Katsuhiko , Dutta Amit , Yamanaka Takayuki , Hatanani Shigeo , Oda Shunri
Published: October 2002

A two-gate single electron memory device with active area of 1.5×10-10 cm2
allows the study of Si/SiO2 interface in nano-scale channels of silicon on insulator
(SOI) and nanocrystalline Si (nc-Si) dots. The basis of this device is a trench (150–600 nm wide)
defined inside a large “inversion” gate electrode into which nc-Si (8±1 nm diameter) can
be deposited by remote plasma enhanced chemical vapor deposition. Device structure is analyzed
with 2-D and 3-D numerical simulation of Poisson's and continuity equations, which show uniform
surface potential of channel. The device design allows for tuning of threshold shifts as well as
controlling the length of active area from 65–165nm with applied gate bias. This allows for
quantifiable threshold shifts for charged interface defects on the channel as well as charge
stored in nc-Si. Threshhold shifts of between 70–120 mV are calculated depending on the location
of charged species along the width of the 30nm wide channel. To study energy levels of single defect
sites, lifetime studies of charged sites are possible with and without deposited nc-Si.
Quantum Computer Using Coupled-Quantum-Dot Molecules
Authors: Wu Nan-Jian , Kamada Masurao , Natori Akiko , Yasunaga Hitoshi
Published: October 2002

We propose a method for implementing a quantum computer using artificial molecules. The artificial molecule consists of two coupled quantum dots stacked along the z direction and one single electron. One-qubit and two-qubit gates are constructed by one molecule and two coupled molecules, respectively. The ground state and the first excited state of the molecule are used to encode the |0> and |1> states of a qubit. The qubit is manipulated by a resonant electromagnetic wave that is applied directly to the qubit through a microstrip line. The coupling between two qubits in a quantum-controlled NOT gate is switched on (off) by floating (grounding) the metal film electrodes. We study the operations of the gates using a box-shaped quantum dot model and numerically solving a time-dependent Schrödinger equation, and demonstrate that the quantum gates can perform quantum computations. The operating speed of the gates is about one operation per 4 ps. The reading operation of the output of the quantum computer can be performed by detecting the polarization of the qubits.
Effect of Impurity at SiO2/Si Interface on 2D Hole Gas
Authors: Fujioka Hiroshi , Noma Hirokazu , Ono Kanta , Oshima Masaharu
Published: October 2002

We investigated the effect of boron penetration through SiO2 on the inversion layer using a two-dimensional hole gas simulator. We found that boron penetration causes serious changes not only in the threshold voltages but also in the average hole depth, which leads to changes in the hole mobility and the inversion layer capacitance. We also found that the boron diffusion length plays an important role in determining the average hole depth.
Plasma-Process-Induced Damage in Sputtered TiN Metal-Gate Capacitors with Ultrathin Nitrided Oxides
Authors: Chen Chi-Chun , Lin Horng-Chih , Chang Chun-Yen , Chao Tien-Sheng , Huang Tiao-Yuan , Liang Mong-Song
Published: October 2002

A comprehensive study on plasma-process-induced damage (P2ID) in sputtered TiN metal-gated devices with 4 nm N2O-nitrided oxide was performed. We found that the TiN metal-gated devices exhibit a significant 8 Å reduction in the effective oxide thickness, due to physical damage caused by sputtering and/or oxide consumption during the postannealing step. We also found that the postdeposition rapid thermal annealing (RTA) temperature affects both the flat-band voltage (V
fb) and the interface state density (D
it). Furthermore, degradation in the gate-oxide integrity caused by severe charging damage by the additional plasma processes in the TiN metal gate process flow was also observed. The P2ID leads to significant degradation in the charge-to-breakdown and a gate leakage current increase, even for the genuinely robust nitrided oxide used in this study. Finally, N2 plasma posttreatment was proposed as an effective method for suppressing the gate leakage current.
Quantitative Secondary Ion Mass Spectrometry Analysis of Carbon and Fluorine Impurities on Silicon Wafers Stored in Polymer Carrier Cases
Authors: Yamazaki Hideyuki , Tamaoki Makiko , Oohashi Masaya
Published: October 2002

We have investigated the carbon and fluoride contaminants on silicon wafers during their storage in quartz-glass boxes equipped with carrier cases made of either polypropylene (PP), polybutylene-terephthalate (PBT), or perfluoroalkoxy polymer (PFA). The adsorbed organic contaminants on the wafer surfaces were identified by time-of-flight secondary-ion mass spectrometry (TOF-SIMS). The concentrations of contaminants on the wafer surface have been measured as a function of wafer storage positions as well as carrier case storage time. For quantitative analyses, secondary-ion mass spectrometry (SIMS) combined with the encapsulation method was employed, and carbon (12C-) and fluorine (19F-) ions were detected. It has been found that the amount of adsorbed contaminants on the surface of silicon wafers depend on both the wafer storage conditions and the carrier case materials.