bluuebunny/crossref_metadata_2025 huggingface dataset:
Single Silicon Atom Detection on a Tungsten Tip
Authors: Shimizu Tetsuo , Tokumoto Hiroshi
Published: October 2002

With a conventional field ion microscope (FIM), we characterized the tip after indentation by a scanning tunneling microscope (STM).
Bright spots are observed at a low applied voltage before the observed voltage of the pole structure of W(110), which are likely to consist of Si atoms.
Next, by the AP with a position detector, we performed the chemical identification of a bright spot in the FIM image.
A single atom is detected only when a pulse voltage is applied.
The mass and the position of the detected atom are simultaneously determined.
The identified mass is that of a doubly charged single Si ion.
The position determined by the AP with a position detector coincides with the disappeared spot in the FIM image after the pulse voltage application.
In other words, the bright spot consists of a single Si atom.
This result suggests that identification of atoms captured on the tip by STM atom manipulation can be realized.
A New Design Scheme for Logic Circuits with Single Electron Transistors
Authors: Ken Uchida Ken Uchida , Kazuya Matsuzawa Kazuya Matsuzawa , Akira Toriumi Akira Toriumi
Published: October 2002

A new design scheme for logic circuits utilizing single electron
transistors (SETs) is proposed. First, logic operations are
implemented in logic trees composed of SETs used as pull-down devices.
Second, the supply voltage to SET logic trees is lower than the gate
voltage swing of SETs. Third, a clock control concept similar to that
of complementary metal-oxide-semiconductor (CMOS) dynamic logic is
utilized. Finally, the output voltages of logic trees are amplified to
the same voltage as the gate voltage swing of SETs by the CMOS
inverters in order to drive the next gates. It is confirmed by the
hybrid simulator of single electron tunneling and SPICE that a SET
logic circuit, a four-way exclusive OR, operates perfectly. It is
concluded that the proposed SET logic is consistent in voltage levels
and is realistic for the hybrid circuits of SETs and CMOS.
Reliability of Single Electron Transistor Circuits Based on Eb/N0-Bit Error Rate Characteristics
Authors: Shimano Satoshi , Masu Kazuya , KazuoTsubouchi KazuoTsubouchi
Published: October 2002

Bit error rate (BER) characteristics of single electron transistor (SET) circuits have
been evaluated using the Monte Carlo simulation. It has been confirmed from the
simulation results that the reliability of the complementary-SET (CSET) inverter is
dominated by the universal E
b/N
0-BER characteristics, where E
b is the bit energy, N
0
the noise power per unit frequency, and BER the bit error rate. In this paper it is
determined from the E
b/N
0-BER characteristics of the CSET circuit, that the CSET
system based on the conventional circuit building method cannot be implemented for
room temperature operations.
Production of Stable Atomic Beam in Electron Beam Evaporation Process
Authors: Ohba Hironori , Shibata Takemasa
Published: October 2002

A metal atomic beam was produced by electron beam heating with high efficiency using a
hearth liner and a porous rod for cerium and gadolinium. While the top surface of the porous rod
was heated by an electron beam, the molten evaporation material surrounding the rod was
transferred to the top surface by capillarity; then the atomic beam was produced from the top
surface. For every evaporation material, an extremely high atomic beam flux with high stability was
obtained even at low input power, without contamination by tungsten atoms from the porous
material.
Frequency-Locked Submillimeter Wave Generation from Josephson Junction Arrays
Authors: Song Insang , Kang Kwang-Yong , Park Gwangseo
Published: October 2002

We fabricated a Josephson junction array with an additional inductive coupling line to
detect the high frequency and power of Josephson self-radiation. The YBa2Cu3O
y
Josephson
junctions are fabricated by a pulsed laser deposition method on bicrystal MgO substrates.
We measured the submillimeter wave and the Josephson self-radiation power in an external
waveguide system. The Josephson junction arrays showed the resistively shunted junction (RSJ)-like current–voltage characteristics and good frequency-locking of Josephson self-radiation.
As the number of Josephson junctions increased, the maximum detected power was increased. We observed the maximum frequency of above 6 THz for Josephson self-radiation in the array with 11 Josephson junctions from the Shapiro steps under
22 GHz irradiation.
Large-Area Uniform Surface Treatment of Polymeric Materials Using a Scanning Plasma Method
Authors: Sung-Chae Yang Sung-Chae Yang , Junichi Yanagi Junichi Yanagi , Kyoichi Yamamoto Kyoichi Yamamoto , Haruo Uyama Haruo Uyama , Hiroshi Fujiyama Hiroshi Fujiyama
Published: October 2002

Applications of the scanning plasma method (SPM) have been investigated for the surface treatment of polymeric materials such as polyethylene terephthalate and polypropylene. Using optical emission spectroscopy, it was found that a uniform plasma with about 140 mm in film width can be obtained due to the transportation effects of E ×B drift in the presence of crossed magnetic field. The plasma treatment of polymeric materials by SPM induces the water contact angle to decrease, i.e., higher wettability, with increasing applied discharge voltage and decreasing the gas pressure. From the experimental results, it was found that SPM is very useful for the surface treatment of polymeric films because uniform and low-temperature surface treatment extending over a large area can be realized.
PbCaTe Films and PbCaTe/PbTe Superlattices Prepared by Hot-Wall Epitaxy
Authors: Ishida Akihiro , Tsuchiya Toshiharu , Ishino NobuyaYoshioka , Fujiyasu Hiroshi
Published: October 2002

PbCaTe films, and PbCaTe/PbTe and CaTe/PbTe superlattices were prepared by hot-wall epitaxy for application to mid- and far-infrared lasers of the 4 to 20 µm range. The
PbCaTe ternary alloy shows good lattice matching with PbTe, and high carrier
concentration films with a band gap wider than 650 meV were obtained by doping Bi and Tl as donor and acceptor impurities, respectively. PbCaTe/PbTe and CaTe/PbTe
superlattices with very thin CaTe layers were also prepared. Optical transmission
measurements were performed for the superlattices. Steplike interband absorption due
to two the dimensional density of states of the superlattices was observed at room
temperature. The absorption edge of the PbCaTe/PbTe superlattices agreed well with
the theoretical values calculated by the envelope-function approximation.
Compression of Electrical Pulses Using Traveling-Wave Field Effect Transistors
Authors: Koichi Narahara Koichi Narahara , Taiichi Otsuji Taiichi Otsuji
Published: October 2002

A novel pulse compression scheme, which uses traveling-wave field effect transistors (TW-FETs) as the core elements, is proposed for the generation of ultrashort electrical pulse signals. The compression is achieved by modulating the amplitude of nonlinear solitary waves propagating along the gate line by the positive feedback established by the “carbon-copy” waves induced on the drain line. This article provides a theoretical description of the scheme, and some results of experimental investigations that characterize wave propagation on the gate line of a TW-FET.
Zero Bias Anomaly and Preferred Surface Grain Orientation of YBa2Cu3O7-δ Ceramics
Authors: Han Xiao , Oka Katsutoshi , Yamada Nobuyoshi , Iri Takeo
Published: October 2002

The zero bias anomaly dependent on the preferred surface grain
orientation of YBa2Cu3O7-δ ceramics has been investigated in the
conductance curve of the tunneling characteristics. A tunnel
junction was fabricated by evaporating Al metal onto the ceramics
sample and then annealed to remove the oxygen-deficient layer. The
preferred orientation and the oxygen deficiency on the surface were
examined based on X-ray diffraction patterns and X-ray
photoelectron spectra. There exist oriented grains with their c-plane
parallel to the ceramics sample surface. These surface layers are
oxygen-deficient. Using the junction fabricated on the oxygen-deficient grains, the zero bias anomaly appears on the dynamic
conductance curve of the tunneling characteristics. This anomaly
disappears when the junction is fabricated after mechanical
polishing of the surface and annealed. One of the sources of zero bias
anomaly is the existence of oxygen-deficient grains on the
YBa2Cu3O7-δ surface.
First Principles Study on Factors Determining Battery Voltages of LiMO2 (M=Ti-Ni)
Authors: Koyama Yukinori , Tanaka Isao , Nishitani Yang-SooKim , HirohikoAdachi HirohikoAdachi
Published: October 2002

In order to evaluate the battery voltages of LiMO2/MO2 systems and to understand the electronic mechanism that determines the voltages, two kinds of first principles calculations are combined, i.e., molecular orbital calculations by the discrete variational (DV)-Xα method
using model clusters and the full-potential linearized augmented plane
wave (FLAPW) band-structure calculations. Electronic structures
obtained by the two methods agree satisfactorily. Two factors that
determine battery voltages are evaluated separately by the
DV-Xα method: 1) the effective electrostatic potential
(Madelung potential) at the Li site, which corresponds to the energy
required to remove a Li ion from LiMO2, 2) the energy of the
highest occupied molecular orbital, which is related to the energy
required to remove an electron. The sum of these two factors
reproduces well the theoretical battery voltages by the FLAPW
method. Moreover, they agree well with experimental open-circuit
voltages.
Molecular Orientational Structures with Macroscopic Helix in Antiferroelectric Liquid Crystal Subphases
Authors: Akizuki Tomoo , Miyachi Kouichi , Takanishi Yoichi , Ishikawa Ken , Takezoe Hideo , Fukuda Atsuo
Published: October 2002

The helical pitch and the optical rotatory power (ORP) were
measured in the subphases of an antiferroelectric liquid crystal.
These measurements clearly indicate the existence of a macroscopic
helical structure with a pitch of several microns. The selective
reflection and ORP in several molecular orientational structures
were simulated using the 4×4 matrix method. A comparison
between the experimental and simulated results clearly denies the
molecular orientational structures based on the clock model, in
which the molecules in these subphases form helical structures
consisting of several layers. A new, modified structure of the
antiferroelectric AF phase was proposed based on ORP in the
smectic-C*-AF phase transition and conoscopy studies. This
modified structure is consistent with a recent resonant X-ray
experiment.
Dependence of Electrically Induced Strain on Orientation and Composition in Pb(ZrxTi1-x)O3 Films
Authors: Sumi Kouji , Qiu Hong , Shimada Masato , Sakai Shinri , Yazaki Shiro , Murai Masami , Moriya Soichi , Miyata Yoshinao , Nishiwaki Tsutomu
Published: October 2002

The effect of orientation and composition on electrically induced strain and relative permittivity of 600-nm-thick Pb(Zr
x
Ti1-x
)O3 (PZT) films was investigated. High permittivity was obtained near the morphotropic
phase boundary (MPB) composition, unaffected by
orientation. For films with mixed textures of [111] and
[100], the electrically induced strain was maximum near
the MPB composition. While the electrically induced
strain showed a tendency to increase with increasing Zr
concentration x in the films with [111] preferred
orientation, for the Pb(Zr0.65Ti0.35)O3 film with [111]
preferred orientation, an electrically induced strain of
0.54% was obtained under an electric field of 250 kV/cm.
Transient Impulse Breakdowns of SF6Gas in Inhomogeneous Electric Fields
Authors: Kawamura Tatsuo , Lee Bok-Hee
Published: October 2002

In this paper, we describe the dielectrics and predischarge developments of gaseous SF6stressed by nonoscillating and oscillating impulse voltages in inhomogeneous fields caused by a metallic protrusion. The breakdown voltage-pressure curves and the formative time lags to breakdown were measured in the gas-pressure range extending from 0.05 to 0.3 MPa. The predischarge processes were simultaneously investigated through measurements of the current induced by moving space charges and photomultiplier records. The predischarge propagates into the gap with a stepwise leader, and the basic physical mechanisms leading to electrical breakdown are the same for nonoscillating and oscillating impulse voltage waveforms. While for the other, the quickly changing macroscopic electric field due to space charges in the gap affects the leader propagation under the oscillating impulse voltage waveform. In the case of negative polarity, the predischarge growth processes at the increasing and decreasing parts of the oscillating wave tail are not very similar. It is inferred that the breakdown at the decreasing part of the oscillating impulse voltage originates from ion depletion due to recombination.
Investigations on the Rotating Electrode Effect on the Ozone Generation Process in a Plate Ozonizer
Authors: Cieplak Tomasz , Yamabe Chobei , Ihara Satoshi , Satoh Saburoh , Cieplak Joanna , Pollo Iwo
Published: October 2002

The effect of electrode rotation on the ozone generation process is presented. An ozonizer with an electrode rotating system might be one possible way to increase ozone-synthesis efficiency. The research presented shows that with electrode rotation the ozone-generation efficiency increases by about 15% compared to an ozonizer with a non-rotating electrode; discharge also becomes more homogenous.
Semiempirical Band Calculation of Pd-Adsorbed SnO2 Surface
Authors: Matsushima Shigenori , Kobayashi Kenkichiro , Kohyama Masanori
Published: October 2002

The electronic structure of a Pd-adsorbed SnO2 (001)
surface is calculated using a semiempirical tight-binding method.
When a Pd atom bridges two oxygen atoms on the SnO2 (001)
surface, bonding and antibonding states arising from the admixture of
Pd 4d and O 2p orbitals are formed around -15 eV and
-8.35 eV. The energy levels of these bonding and antibonding
states are overlapped with those of the valence and conduction bands.
Nonbonding states originating from Pd 4d are calculated to be
-9.2 eV and are located near the bottom of the conduction band of
SnO2. The Fermi level of -8.37 eV is pinned at the nonbonding
states with a large state density. When two Pd atoms are bound to two
oxygen atoms on SnO2 (001), Pd-related states exhibit a bandlike
character in spite of less than one monolayer coverage.
Comparison of Deposition Characteristics between Triethyl and Trimethyl Borates in an Atmospheric Pressure Chemical Vapor Deposition Equipment with Tetraethyl Orthosilicate and O3
Authors: Yamamoto Yoshito , Ikakura Hiroshi , Ohgawara Shoji , Furukawa Masakazu
Published: October 2002

The deposition characteristics of triethyl borate (TEB) and
trimethyl borate (TMB) vapors are compared to investigate of boron
concentration uniformity and profiles in borophosphosilicate glass
(BPSG) films. Film deposition is carried out in an atmospheric
pressure equipment with tetraethyl orthosilicate (TEOS) and ozone
(O3) under at standard condition and four process parameters are
varied around the standard condition. Uniformity values obtained
with the TMB vapor at a bubbling temperature of 10°C are one-third
that with the TEB vapor at the same bubbling temperature, and
uniformity changes due to process parameter variations from the
standard condition with the TMB vapor are also smaller since the
TEB vapor is cleaved by O3 at lower temperature. These results
indicate that the deposition characteristics for uniformity using
TMB vapor are much better. However, a decrease in the boron
concentration profile in films with the TMB vapor is observed
between a silicon and silicon-dioxide interface. This decrease is
estimated to be due to the fact that TMB bubbling N2 flow rate to
suppress the vaporization rate with TMB's higher vapor pressure is
one order of magnitude lower than TEB bubbling N2 flow rate.
Suppression of TMB vapor to a desired vapor pressure was achieved
by cooling the TMB bubbler at -25°C. Then, a uniform profile of
the TMB vapor was obtained, which was equivalent to the results at
10°C.
Growth and Temperature Dependence of Optical Properties of Er Doped and Undoped n-Type InSe
Authors: Gürbulak Bekir , Yildirim Muhammet , Ateş Aytunç , Doğan Seydi , Yoğurtçu Yahya Kemal
Published: October 2002

n-InSe and Er doped n-InSe (n-InSe:Er) single crystals were grown by the modified
Bridgman-Stockbarger method. The prepared InSe and InSe:Er single crystal ingots were 12 mm in diameter and about 80 mm in length. The ingots had no cracks or voids on the
surface. The absorption measurements were carried out for n-InSe, and
n-InSe:Er samples in
the temperature range of 10–320 K. Binding energies of n-InSe and
n-InSe:Er were calculated
to be 20.5 meV and 21.0 meV respectively. The direct band gaps were estimated to be
1.339 eV, 1.289 eV and 1.256 eV in n-InSe and were 1.338 eV,
1.288 eV and 1.253 eV in n-InSe:Er at 10 K, 200 K and 300 K, respectively. E
o (1.247 eV) obtained from the Urbach
rule is nearly equal to the energy gap of n-InSe at 300 K.
Separation between Surface Adsorption and Reaction of NH3 on Si(100) by Flash Heating
Authors: Watanabe Takeshi , Sakuraba Masao , Murota TakashiMatsuura
Published: October 2002

Separation between surface adsorption and reaction in atomic-layer nitridation of
Si(100) in an NH3 environment (50–500 Pa) has been investigated by flash heating using an
ultraclean low-pressure cold-wall reactor system. The N atom concentration (n
N) on Si(100) at
400°C initially increases with flash heating by light irradiation of 60 J/cm2 per shot and then
tends to saturate at a certain value (∼2.7×1015 cm-2). It has been observed that in nitridation
with flash heating, a Langmuir-type physical adsorption layer is formed on Si(100), similar to
thermal nitridation without flash heating, and reacts at a certain rate. The physically adsorbed
NH3 coverage is the same for both cases with and without flash heating. The flash heating
markedly increases the reaction efficiency of physically adsorbed NH3 as well as the
saturation value of n
N. The bonding characteristics observed by X-ray photoelectron
spectroscopy in the cases with and without flash heating were almost similar when n
N was the
same.
Control of Light Transmission in Polymer Gels by Stimuli-Responsive Guest Microparticles
Authors: Suzuki Atsushi , Sanda Kinichi
Published: October 2002

We developed a soft, optical material of polymer gels with the capability of controlling the visible light transmission in response to temperature change. The polymer gel is a weakly cross-linked thermostable network of poly(acrylamide), which is slightly impregnated with thermoresponsive gel microparticles of poly(N-isopropylacrylamide). It was found that the light transmission can be reversibly controlled only by adjusting the temperature; the transmitted light intensity rapidly and continuously decreases with increasing temperature. The system can, therefore, behave as an optical “shutter”. The phenomena were attributed to the local structural change induced by the volume phase transition of guest microparticles. The light transmission properties depend on the interpenetrating state of guest microparticles immobilized in host networks, which are permanently introduced during gelation. The relaxation time depends on both the final and the initial temperatures. Static and kinetic properties are discussed phenomenologically on the basis of the volume phase transition of guest microparticles under mechanical constraint.
Electron Kinetics of Ionization Waves in Helium Positive Columns
Authors: Sirghi Lucel , Ohe Kazuyuki , Popa Gheorghe
Published: October 2002

Electron kinetics related to ionization waves is discussed using the results of temporally and radial-spatially resolved Langmuir probe measurements during propagation of an artificially excited ionization wave packet along a helium positive column at 0.55 Torr pressure and 200 mA discharge current. The results show a strong interdependence between the axial and radial electric field fluctuations and the electron energy distribution fluctuations. Fluctuations in the electron energy distribution function related to the ionization waves revealed a complex energy spectrum whose low (0–10 eV) and high (10–25 eV) energy regions oscillate with opposite phases.
Diagnostic of Surface Wave Plasma for Oxide Etching in Comparison with Inductive RF Plasma
Authors: Kokura Hikaru , Yoneda Shinichi , Nakamura Keiji , Mitsuhira Noriyuki , Nakamura Moritaka , Sugai Hideo
Published: October 2002

Surface wave plasma (SWP) and inductively coupled plasma (ICP) reactors are high plasma density, unmagnetized sources that show promise for use in next-generation etching processes. We compare the 2.45 GHz SWP with the 13.56 MHz ICP in terms of the radical composition in C4F8/Ar discharges and the electron energy distribution function (EEDF). A comparison of the two plasmas was carefully made in an identical plasma vessel at the same wall temperature where an antenna coupler on a quartz plate was changed from an expanded waveguide for SWP to a loop coil for ICP. Reactive species measurement at the same electron density under the same gas conditions showed marked differences. First, the dissociation degree of C4F8at the same electron density is higher in ICP than in SWP. Second, neutral radical densities (CF3, CF2) at the same electron density are several times higher in SWP than in ICP, and ICP has a high F radical density. Third, as regards ionic composition, ICP contains more Ar+and less fluorocarbon ions (CmFn+), while large molecular ions (C2F4+, C3F3+, C3F5+) exist in SWP. In conclusion, ICP is more dissociative than SWP at the same electron density. This result is tentatively attributed to the difference in the EEDFs of the two plasmas, since optical emission spectroscopy of Ar I suggests 1.5–2 times more high-energy (>14 eV) electrons in ICP than in SWP.
Properties and Degradation of Polarization Reversal of Soft BaTiO3 Ceramics for Ferroelectric Thin-Film Devices
Authors: Thongrueng Jirawat , Tsuchiya Toshio , Masuda Yoichiro , Fujita Shigetaka , Nagata Kunihiro
Published: October 2002

Soft BaTiO3 ceramics having a very low coercive field of 65 V/mm were prepared by substituting 9 mol% Hf–Zr for the Ti-site of BaTiO3, for applications to ferroelectric thin-film devices. Electrical
properties of the soft BaTiO3 ceramics were measured and compared with those of normal BaTiO3
ceramics. By substituting Hf–Zr for Ti-site, the phase transition temperatures were controlled, and we
could select the preferred crystal structure from the tetragonal, orthorhombic and rhombohedral phases
at room temperature. In addition, the preparation and characterization of the soft BaTiO3 thin-films
using a sol-gel process were carried out.
Optically Induced Persistent Charge Storage Effects in Self Assembled InAs Quantum Dots
Authors: Finley Jonathan J. , Skalitz Matthias , Arzberger Markus , Zrenner Artur , Böhm Gerhard , Abstreiter Gerhard
Published: October 2002

Resonant optical excitation of the quantum dot (QD) ensemble produces a strong increase of the lateral resistance of a spatially separated InGaAs n-channel. This is shown to arise from the preferential storage of electrons within the QD layer. The induced photoeffect is persistant over timescales of many hours at 140 K and can be controllably erased by injecting holes into the QD layer from a separate p-contact.
The magnitude of the induced photo-effect is found to be sensitive to the excitation energy with a number of resonances observed which reflect inelastic excitation of the QD ensemble.
By performing power dependent measurements a similar resonance is observed in the device switching time after illumination. The potential operation of the device as a novel, wavelength selective, optical memory is suggested.
Effect of Excess Lead Addition on Processing of Sol-Gel Derived Lanthanum-Modified Lead Zirconate Titanate Thin Film
Authors: Hirano Tomio , Kawai Hiroki , Suzuki Hisao , Kaneko Shoji , Wada Tatsuya
Published: October 2002

Sol-gel-derived lanthanum-modified lead zirconate titanate (PLZT) thin films with a La/Zr/Ti
ratio of 10/65/35 and a lead lanthanum titanate (PLT) thin seeding layer were successfully
deposited on an indium tin oxide (ITO)-coated soda lime glass substrate at 500°C. Effects of
excess lead addition of different concentrations in the precursor solution on the electrical
properties of the resultant PLZT thin films were investigated. As a result, the relative
permittivity increased and the dissipation factor decreased with the increase of excess lead
concentration. Excess lead of 30 mol% was indispensable for obtaining PLZT thin film with
good ferroelectricity. In addition, the resultant films showed more than 60% transmittance in
the visible region.
Synthesis and Ferroelectric Properties of Ni-Modified 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 Solid Solution System
Authors: Bae Kim Gang , Man Jung Jong , Won Choi Seong
Published: October 2002

The correlation between the sintering temperature and ferroelectric
properties of Ni-modified 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3
ceramics has been investigated. The stability of the perovskite phase was
studied as a function of sintering temperature. The influence of NiO
addition on the microstructural, dielectric and pyroelectric properties
of the ceramics is investigated by varying the additive amounts of NiO and
the sintering temperature. The optimum conditions for obtaining samples
with improved ferroelectric properties are at a sintering temperature
of 1050°C and a sintering time of 2 h by a nominal addition of
0.4 wt% NiO. The dielectric and pyroelectric peak temperatures are
nonlinearly shifted to a lower temperature with the addition of small
amounts of NiO. The diffuseness of the phase transition is almost
constant in dopant content.
Structural and Electrical Properties of Crystalline TiO2 Thin Films Formed by Metalorganic Decomposition
Authors: Fukuda Hisashi , Namioka Seigo , Miura Miho , Ishikawa Yoshihiro , Yoshino Masaki , Nomura Shigeru
Published: October 2002

Titanium oxide (TiO2) thin films were formed on a Si substrate by metalorganic
decomposition at temperatures ranging from 600°C to 1000°C. As-deposited films were in the
amorphous state and were completely transformed after annealing at 600°C to a crystalline
structure with anatase as its main component. During crystallization in oxygen atomosphere, a
reaction between TiO2 and Si occurred at the interface, which resulted in the formation of a thin
interfacial SiO2 layer. Capacitance-voltage measurement showed good dielectric properties with
a maximum dielectric constant of 76 for films annealed at 700°C. For the crystallized TiO2
films, the interface trap density was 1×1011 cm-2eV-1, and the leakage current
was 1×10-8 A/cm2 at 0.2 MV/cm. The modified structure of TiO2/SiO2/Si is expected to be suitable for the
dielectric layer in an integrated circuit in place of SiO2 or
Si3N4 films.
Characterization of Dielectric Etching Processes by X-Ray Photoelectron Spectroscopy Analyses in High Aspect Ratio Contact Holes
Authors: Joubert Olivier , Czuprynski P.
Published: October 2002

X-ray photoelectron spectroscopy (XPS) analyses of high aspect ratio structure etched in SiO2 and
organic low dielectric constant materials are presented. Analyses are performed after etching using
commercial etching tools and standard processes developed for 0.18 µm design rules. Using
electron shadowing by adjacent features, differential charging of insulating features and angle-resolved
XPS, it is possible to separate the contributions originating from the sidewalls and bottoms
of high aspect ratio contact holes. Correlation between XPS analyses and etch mechanisms are also
discussed.
Selective Growth of GaAs on GaAs (111)B Substrates by Migration-Enhanced Epitaxy
Authors: Keita Suzuki Keita Suzuki , Masahiro Ito Masahiro Ito , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

Selective epitaxial growth of GaAs on GaAs (111)B substrates masked by SiO2 has been demonstrated by using migration-enhanced epitaxy (MEE) with annealing after deposition of either Ga or As4. When annealing is performed after Ga deposition, no polycrystalline GaAs is formed on the SiO2 mask and the surface of the epitaxial layer grown in the window region is very smooth and uniform, whereas polycrystalline deposition occurs when the annealing is performed after As4 deposition. These results indicate that complete selectivity is more easily obtained by annealing after Ga deposition rather than As4 deposition. By using this method successful selective growth of GaAs has been achieved at substrate temperature around 590°C. Ga adatoms deposited on the SiO2 mask seem to evaporate or diffuse into the window region during the Ga deposition and annealing period. The conditions for successful selective growth has been established as a function of substrate temperature and Ga flux, so that smooth epitaxial layers are grown reproducibly. We also discuss the surface diffusion of Ga atoms on the SiO2 mask.
Evaluation of Optical Gain Properties of GaInAsP/InP Compressively Strained Quantum-Wire Lasers
Authors: Takashi Kojima Takashi Kojima , Suguru Tanaka Suguru Tanaka , Hideo Yasumoto Hideo Yasumoto , Shigeo Tamura Shigeo Tamura , Shigehisa Arai Shigehisa Arai
Published: October 2002

The gain spectral characteristics of 1.5-µm-wavelength GaInAsP/InP compressively strained quantum-wire lasers with wire widths of 20 nm and 25 nm, fabricated by electron-beam lithography and two-step organometallic vapor phase epitaxial growth, were measured at a temperature of 100 K and were compared with those of quantum-film lasers fabricated on the same wafer. It was found, for the first time, that the material gain spectrum of quantum-wire lasers is narrower than that of the quantum-film laser. Moreover, the origin of this narrow gain spectral property of the quantum-wire lasers was theoretically investigated and explained in terms of the twofold longer intraband relaxation time in the quantum-wire structure.
Theoretical Analysis of a Radio Frequency Excited Slab CO2 Laser
Authors: Matsuoka Naoya , Yamaguchi Shigeru , Nanri Kenzo , Fujioka Tomoo
Published: October 2002

Theoretical analysis of a radio frequency (RF) excited slab CO2 laser was carried out,
considering not only the bulk plasma region but also the plasma boundary layer. To
evaluate laser characteristics, electron density and electron temperature were estimated.
The result of computation indicates that electron density and electron temperature
would be higher in the boundary layer than in the bulk plasma region. Using such
conditions, small-signal gain was computed to be approximately 1.5%/cm in the bulk
plasma region and 0.5%/cm in the boundary layer. Thus, the gain in the boundary layer
is lower than that in the bulk plasma region, but the boundary layer can sufficiently act
as a gain medium as well as the bulk plasma region.
Induced Defects and Increase of Second-Order Nonlinearity in Ultraviolet-Poled GeO2–SiO2 Glass
Authors: Ohama Motoshi , Fujiwara Takumi , Ikushima Akira J.
Published: October 2002

We report on enhancement by thermal defects control of the second-order optical
nonlinearity in GeO2–SiO2 glass induced by ultraviolet (UV) poling. The present work is based on the previous results which suggest GeE' centers as the most relevant ingredient to produce the induced nonlinearity, and heat treatment in a vacuum before UV poling has been found to increase the induced second-harmonic generation (SHG). The result is thought to be related to an increase of oxygen deficient defects, which function as precursors of the photoinduced GeE' centers. To obtain larger d coefficient, optimization of pre-heat treatment conditions, temperature and time duration, have been investigated. The largest value of d
33 coefficient thus far obtained is 5.1±0.2 pm/V in UV-poled GeO2–SiO2 glass of 15 mole% GeO2 content with the pre-heat treatment at 1200°C for 5 h, which exceeds d
13, the second largest coefficient of LiNbO3.
Characteristics of NdBa2Cu3O7-δ Josephson Junctions Fabricated by Deca-Nanoscale Focused Ion Beam
Authors: Ohnishi Katsu , Miyahara Kazunori , Enomoto Youichi
Published: October 2002

Grain boundary Josephson junctions were fabricated on microgrooves formed
by a focused ion beam (FIB) system with a nominal ion beam diameter of 10 nm. Among the 40 junctions fabricated under the constant condition, 29 working
junctions exhibit resistively-shunted-junction-type current–voltage characteristics
and follow empirical scale rule of linear relation between I
c
R
n and I
c
1/2. For R
n,
the distribution is Gaussian-type and 1σ is estimated to be 40%. On the other
hand, I
c is distributed with three peaks and 1σ is estimated to be 60%. The peak
separation in the I
c distribution indicates the existence of different types of grain
boundaries, corresponding to three kinds of tilting angles with
lattice matches.
Lithography Simulator for Electon Beam/Deep UV Intra-Level Mix & Match
Authors: Ryoichi Inanami Ryoichi Inanami , Tetsuro Nakasugi Tetsuro Nakasugi , Shinji Sato Shinji Sato , Shoji Mimotogi Shoji Mimotogi , Satoshi Tanaka Satoshi Tanaka , Kazuyoshi Sugihara Kazuyoshi Sugihara
Published: October 2002

We have developed an electron beam/deep UV (EB/DUV) intra-level
mix & match (IL M&M) lithography simulator.
In the simulator,
for EB and DUV exposure pattern to be exposed in the same resist layer
in IL M&M lithography process,
(1) energy distributions deposited by the EB and the DUV exposures
are calculated in respective simulators separately.
(2) The two energy distributions are blurred respectively
by the Gaussian convolution whose standard deviation is called
a lithography process parameter, ΔL.
(3) The two blurred energy distributions are superposed on each other.
(4) Development calculation is performed.
The propriety of these calculations was confirmed by contrast
with a corresponding experiment.
By demonstrating two examples of the application of the simulator,
the simulator is shown to be a helpful tool for precognition of
results obtained by applying the EB/DUV IL M&M lithography process.
The simulator is essential for optimizing the various conditions
in the EB/DUV IL M&M lithography.
Development of Highly Accurate X-Ray Mask with High-Density Patterns
Authors: Shimada Masaru , Tsuchizawa Tai , Uchiyama Shingo , Ohkubo Takashi , Itabashi Seiichi , Okada Ikuo , Ono Toshiro , Oda Masatoshi
Published: October 2002

Highly accurate X-ray masks with high-density patterns have been
newly developed. SiC film is used as a membrane and Ta film
deposited by electron cyclotron resonance (ECR) sputtering method is
used as an absorber. Ru film is deposited as an intermediate layer
between the membrane and the absorber to prevent the distortion
caused by the fabrication of high-density patterns. A membrane
process in which the absorber is patterned after back-etching and a
distortion compensation method by electron beam (EB) writing are
adopted to reduce pattern displacement. By combining these
techniques, highly accurate X-ray masks with high-density patterns,
which correspond to 4-Gbit-class dynamic random access memory (DRAM)
pattern density, can be fabricated with distortions less than 40 nm.
A New Approach to Reducing Line-Edge Roughness by Using a Cross-Linked Positive-Tone Resist
Authors: Yamaguchi Toru , Namatsu Hideo , Nagase Masao , Yamazaki Kenji , Kurihara Kenji
Published: October 2002

We propose a cross-linking technique as a new approach to reducing the line-edge roughness
(LER) of resist patterns. In addition, we also develop a cross-linked positive-tone resist called
the suppressed aggregate extraction development (SAGEX) resist, based on this technique.
Our key approach to reducing the LER is the suppression of the aggregate extraction
development, which causes LER. We demonstrate successful suppression of the aggregate
extraction development by cross-linking polymers in the surrounding regions and by reducing
the difference between dissolution rates inside and outside the aggregates, and clarify that the
LER of the resist patterns in the SAGEX resist is reduced.
Giant Magnetoresistance Effect in CoFeB/Cu/CoFeB Spin Valves
Authors: Shirota Yoshihiro , Tsunashima Shigeru , Imada Ryuji , Nomura Yoshihisa , Iwata Satoshi , Jimbo Mutsuko
Published: October 2002

NiO/CoFeB/Cu/CoFeB spin valves with B content of 0 to 10 at.% were prepared to
investigate the dependence of the giant magnetoresistance(GMR) effect on the thickness of free
magnetic layers. In the spin valves, GMR effects were observed even when the free magnetic layers
were very thin, 1 or even 0.5 nm. For lower B content, the magnetoresistance (MR) ratio rapidly
increased with the increase of free magnetic layer thickness, while for higher B content, the MR ratio
was maximum at the thickness roughly equal to the mean free path of electrons in the magnetic layers.
By using the Camley-Barnas model, the value of the MR ratio and the resistivity can be consistently
explained if the specular reflection of electrons is considered at the interface between magnetic and
nonmagnetic layers.
Tip-Scanning Dynamic Force Microscope Using Piezoelectric Cantilever for Full Wafer Inspection
Authors: Chu Jiaru , Maeda Ryutaro , Itoh Toshihiro , Suga Tadatomo
Published: October 2002

In this study we demonstrate the structure of a new dynamic
force microscope (DFM) compatible with full wafer inspection. It
is a tip-scanning-type DFM based on a piezoelectric micro-cantilever
integrated with a conical tip as a force sensor. The piezoelectric
micro-force sensor is mounted on top of a tube scanner. The sample
is put on the sample stage facing the tip. The novel DFM has proven
to be stable for probing the surface of full wafers with a vertical
resolution of about 0.12 nm. The design and performance of the
novel tip scanning DFM is explained in detail in this report.
Manipulations of Densities and Sizes during Self-Assembling Quantum Dots in Metal-Organic Vapour Phase Epitaxy
Authors: Seifert Werner , Johansson Jonas , Carlsson Niclas
Published: October 2002

Densities and sizes of self-assembled 3-dimensional islands were studied in dependence of
their deposition conditions. The materials system for more detailed studies was InP/GaAs,
deposited by low-pressure metal-organic vapour phase epitaxy (MOVPE). The densities of
stable islands follow very well the simple proportionality ρ=const·R/D,
where R= deposition rate and D=the temperature
dependent surface diffusion coefficient. The sizes of the 3-dimensional islands show
inverse behaviour, what is to explain as an effect of distribution of the available material
over the number of islands present at the surface. The bimodality in the
shapes of 3-dimensional islands of InP on GaAs is strongly affected by deposition
temperature and deposition rate. High temperatures/low deposition rates favour the
formation of an almost pure population of fully developed islands with high aspect ratios and
steep {111} and {110} facets. Low temperatures and high deposition rates favour the
population of small, low aspect ratio islands with more flat facets. A comparison with other
Stranski-Krastanow systems shows in general similar dependencies.
Growth of 100-mm-Diameter <100> InP Single Crystals by the Vertical Gradient Freezing Method
Authors: Asahi Toshiaki , Kainosho Keiji , Kamiya Tetsuo , Nozaki Tatsuya , Matsuda Yuko , Oda Osamu
Published: October 2002

100-mm-diameter <100> undoped InP single crystals were grown
by the vertical gradient freezing (VGF) method using a high-pressure
furnace. In order to reduce the temperature fluctuation in the furnace
for preventing twinning during crystal growth, we investigated the gas
flow in the furnace by a computer simulation. The simulation results
showed that the gas flow was quite unstable because of the collision
between the gas and the hot-zone or other gas flows. After we
developed a hot-zone to control the gas flow, the temperature
fluctuation near the seed crystal reduced from ±0.3°C to
±0.03°C. The axial temperature gradient was lower than
10°C/cm and the growth rate was higher than
0.4 mm/h. Twin-free 100-mm-diameter single crystals could be obtained
for the first time under these conditions. The average EPD(Etch Pit
Density) of the grown crystals was about 2000 cm-2, less than
that of the conventional 75-mm-diameter InP LEC (liquid encapsulated
Czochralski) crystals.
Raman Intensity of Phonon Modes in InGaAsP Quaternary Alloys Grown on (100) InP in the Region of Immiscibility
Authors: Touko Sugiura Touko Sugiura , Nobuyasu Hase Nobuyasu Hase , Yasuhiro Iguchi Yasuhiro Iguchi , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

The Raman intensities of optical phonon modes in In
x
Ga1-x
As
y
P1-y
quaternary alloys lattice matched to (100) InP are studied in the compositional region of immiscibility. The peak intensity as well as the integral intensity of each phonon modes are investigated in terms of the relative density of corresponding bonds. It was found that the integral intensity is well interpreted in terms of the bond density. The replacement of a gallium atom with an indium atom produces a remarkable variation in the peak intensity.
Ruthenium Films Prepared by Liquid Source Chemical Vapor Deposition Using Bis-(ethylcyclopentadienyl)ruthenium
Authors: Aoyama Tomonori , Eguchi Kazuhiro
Published: October 2002

Ruthenium (Ru) films were deposited by liquid source chemical vapor deposition
using bis-(ethylcyclopentadienyl)ruthenium (Ru(C2H5C5H4)2). The crystalline structure,
resistivity and residual impurities in the Ru films were investigated. The Ru films were
polycrystalline and had a columnar structure; they showed a low resistivity of about 20 µΩ cm,
which is sufficiently low for them to be used as capacitor electrodes.
Imaging of the DNA (deoxyribonucleic acid) Double Helix Structure by Noncontact Atomic Force Microscopy
Authors: Maeda Yasushi , Matsumoto Takuya , Tanaka Hiroyuki , Kawai Tomoji
Published: October 2002

Noncontact atomic force microscopy (NC-AFM) has been employed in order to observe double-stranded DNA (deoxyribonucleic acid) on a Cu(111) surface. In-situ tip improvement was found to be effective for the NC-AFM measurement. The authors have obtained high-resolution images of double-stranded DNA including the DNA double helix structure using the shape-controlled tip.
High-Performance Diamond Metal-Semiconductor Field-Effect Transistor with 1 µm Gate Length
Authors: Umezawa Hitoshi , Tsugawa Kazuo , Yamanaka Sadanori , Takeuchi Daisuke , Okushi Hideyo , Kawarada Hiroshi
Published: October 2002

High-performance metal-semiconductor field-effect transistors (MESFETs) using the p-type surface conductive layer on homoepitaxial diamond are demonstrated. The maximum transconductance is 110 mS/mm, which is the highest value ever reported in diamond FETs. This value exceeds the normal transconductance of a Si–metal-oxide semiconductor field-effect transistors (MOSFET) with equivalent gate length. The transconductance of the present diamond FETs is proportional to the reciprocal of gate length. Accordingly, the characteristics can be improved by the refinement of gate length. By using an appropriate FET fabrication process, it is expected that the transconductance of a diamond MESFET exceeds 500 mS/mm at gate lengths less than 0.2 µm.
Laser Properties at 1.06 µm for Nd:GdVO4 Single Crystal Pumped by a High Power Laser Diode
Authors: Zhang Huaijin , Meng Xianlin , Zhu Li , Liu Junhai , Wang Changqing , Shao Zongshu
Published: October 2002

In this letter, we report the measurements of the polarization
absorption spectra, polarization emission spectra and laser properties
of Nd:GdVO4 crystal. The highest output power of up to 14.25 W at
1.06 µm has been achieved with a 4 mm thick Nd:GdVO4 crystal sample when it
is pumped by a 26 W cw fiber-coupled laser diode array. The light-light
conversion efficiency is 54.8%. The comparing laser experiments of
Nd:GdVO4 with Nd:YVO4 are also carried out by using the same
laser cavity.
GaN-Based Laser Diodes Processed by Annealing with Minority-Carrier Injection
Authors: Miyachi Mamoru , Ota Hiroyuki , Kimura Yoshinori , Watanabe Atsushi , Tanaka Toshiyuki , Takahashi Hirokazu , Chikuma Kiyofumi
Published: October 2002

Minority-carrier injection was used to activate the acceptor
dopant of GaN-based laser diodes. Lasing was observed in samples
treated at temperatures above 350°C. The threshold current
and current density were 690 mA and 13.8 kA/cm2,
respectively. The lasing characteristic was slightly better than that
of devices fabricated by conventional thermal annealing. The devices
were repassivated by additional annealing in an open-circuit
configuration, and then reactivated by the present method. Laser
oscillation was obtained on the “reactivated” samples with no
significant change in threshold current.
THz Radiation from Intracavity Saturable Bragg Reflector in Magnetic Field with Self-Started Mode-Locking by Strained Saturable Bragg Reflector
Authors: Liu Tze-An , Huang Kai-Fung , Pan Ci-Ling , Liu Zhenlin , Ono Shingo , Ohtake Hideyuki , Sarukura Nobuhiko
Published: October 2002

We demonstrate a new configuration for intracavity generation of THz radiation.
A magnetic-field-biased saturable Bragg reflector (SBR) located inside the femtosecond
laser cavity is the emitter, while a strained saturable Bragg reflector (SSBR) achieves
self-started mode-locking without focusing. The calibrated power of the emitted THz
radiation is estimated to be approximately 45 nW with a peak frequency at 0.72 THz and
width of approximately 0.7 THz under a 0.88 T magnetic field. The quadratic dependence
of THz-radiation power by the SBR on the magnetic field is also observed for the first time.
A Lithium Carboxylate Ultrathin Film on an Aluminum Cathode for Enhanced Electron Injection in Organic Electroluminescent Devices
Authors: Ganzorig Chimed , Fujihira Masamichi
Published: October 2002

The effects of new insulating materials of lithium fluoride and lithium carboxylates at an
aluminum cathodic interface on the performance of organic electroluminescent (EL)
devices are described. Three different cathode interface materials are used: lithium salts of
fluoride, acetate, and benzoate. We compare the current density–voltage (I–V) and the
luminance–voltage (L–V) characteristics of the devices with Al/lithium carboxylates with those of the devices with Al/LiF or an Al cathode. We find that the bilayer cathodes with lithium carboxylates exhibit better device performance than the cathodes with LiF or the Al
cathode itselt. In particular, the device with lithium benzoate gives the best performance of
all the devices studied. The improvements are attributed to the lowering in work function of
the cathode due to lithium metal formation by the higher reactivity of lithium carboxylates
than LiF, with hot Al atoms impinging on these insulating materials.
An Approach to Achieve Intense Photoluminescence of GaN
Authors: Shen Xu-Qiang , Aoyagi Yoshinobu
Published: October 2002

A method to achieve intense photoluminescence (PL) of GaN film grown on Al2O3(0001)
substrates by gas-source molecular beam epitaxy (GSMBE) is proposed. It was found that the PL
intensity of GaN film could be greatly enhanced by In doping during GaN growth. The PL
intensity ratio of GaN:In/GaN at room temperature was 35 times stronger in magnitude, while the
GaN luminescence wavelength was kept constant.
Effects of Chemical Interaction between Ta and SiOF on the Crystallinity of Cu and Ta in Cu/Ta/SiOF Films
Authors: Kyoung-Woo Lee Kyoung-Woo Lee , Seoghyeong Lee Seoghyeong Lee , Sung-Hoon Yang Sung-Hoon Yang , Young-Il Kim Young-Il Kim , Jong-Wan Park Jong-Wan Park
Published: October 2002

Interactions between Ta and SiOF films were investigated. The effect of these interactions on the crystallinity of Cu and Ta films was also examined. It was found that much a rougher interface was formed at the Ta/SiOF interface than at the Ta/SiO2 interface. This clearly resulted from a strong interaction between Ta and SiOF occurring through the defluorination of SiOF film during Ta sputter deposition. Ta oxides and fluorides were observed to form at the interface of Ta/SiOF, which resulted in the degradation of the Ta (002) texture. Furthermore, the degradation of Ta crystallinity led to the reduction of the Cu (111) texture by causing a deficiency in interfacial heteroepitaxiality.