bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Waveguide Properties of Virgin Microscope Slide Glass
Authors: Itoh Kiminori , Niikura Hiroshi , Odawara Osamu , Masayuki Murabayashi Masayuki Murabayashi
Published: February 2005

Virgin microscope-slide glass made of soda glass functions as optical waveguides (OWGs) without further treatment. This is because recent soda glass substrates for microscope slides are produced by the float method, and hence, the slides are doped with Sn ions on one side. The slide glass was examined in terms of effective refractive index, distribution of the Sn ion with secondary ion mass spectroscopy (SIMS), sensitivity for monitoring surface species, and annealing properties.
Ferroelectric Domain Structure and Internal Bias Field in DL-α-Alanine-Doped Triglycine Sulfate
Authors: Noriyuki Nakatani Noriyuki Nakatani
Published: February 2005

Single crystals of ferroelectric triglycine sulfate (TGS) have been grown from solutions containing 10 and 30 mol% of DL-α-alanine. Crystal form, domain structure and distribution of internal bias field E
b in these DL-α-alanine-doped triglycine sulfate: (DLATGS) crystals were investigated. Although the crystal form is influenced by the doping, it shows the symmetry of 2/m similar to pure TGS. The intensity and direction of E
b distinctly depend on the crystal growth sector. The directions of E
b in matching sectors in both b sides of the seed crystal are opposite to each other. Hence the domain structure has a mirror symmetry normal to the b-axis. These features of DLATGS are plainly explained by considering the chirality of alanine and the already-known properties of LATGS.
Structural Analysis of the Formation of CuInSe2
Authors: Nomura Shigetaka , Matsushita Hiroaki , Takeo Takizawa Takeo Takizawa
Published: February 2005

The mechanism of the phase change from Cu2-x
Se to CuInSe2 by the absorption of indium selenide is analyzed in terms of the simulation of X-ray diffraction. The crystal structure of Cu2-x
Se is proposed on the basis of zincblende structure. The simulated X-ray diffraction patterns indicate that more than half of the anion sites are randomly occupied by selenium atoms with the cation sites being fully occupied with copper atoms in the crystal structure of Cu2-x
Se which is regarded as a frame structure of CuInSe2.
Resonance-Enhanced Multiphoton Ionization Study of NO Scattering from a Corrugated Si(100) Surface with Oxygen Coverage
Authors: Miyake Tatsuya , Sakai Masahiro , Kato Hiroyuki , Nakamura Tetsurou , Namiki Akira , Kamba Hideto , Suzaki Tetsuo
Published: February 2005

The resonance-enhanced multiphoton ionization (REMPI) technique has been used to probe the dynamics of NO scattering from oxygen-covered Si(100) as a function of incident beam energy E
i and incident angle θi. A direct inelastic scattering process as well as a trapping-desorption process was observed to occur even for the lowest incident energy available in our apparatus, 0.09 eV. Considerable loss in the peak velocity was found to be E
i-dependent for the direct inelastic component scattered at the specular angle. The angular width of the scattering lobe increased with increasing E
i. These facts are qualitatively explained in terms of the surface corrugation.
Fundamental Features of Plasma Impedance in Planar Radio-Frequency Discharges
Authors: Shigehiko Nonaka Shigehiko Nonaka
Published: February 2005

The most fundamental expressions of plasma impedance for radio-frequency (RF) discharges between a pair of planar electrodes were obtained theoretically on the basis of our theoretical determination of the plasma density in RF discharges. Several characteristic features of the impedance were also disclosed along with two universal critical conditions that determined one of the features. In general, the reactance component was usually capacitive in RF discharges, which arose from the RF power balance in plasma. In this theory, the plasma was assumed to be uniformly produced between electrodes. The theory may be applicable to nonperturbative measurements of the plasma parameters, electron number density and electron energy loss.
Reconstruction of Edge-Plasma Density Profiles by Neutral Beam Probe Spectroscopy
Authors: Komori Akio , Yonesu Akira , Nagai Shingo , Mizuuchi Tohru , Harada Mitsuru , Matsuura Hiroto , Sano Fumimichi , Zushi Hideki , Sudo Shigeru , Nakasuga Masahiko , Obiki Yoshinobu Kawai
Published: February 2005

Thermal neutral beam probing combined with a spectroscopic technique is numerically developed to reconstruct electron-density profiles of edge plasmas. Although the reconstruction has been performed by assuming all beam atoms to have a thermal velocity, the influence of a beam-velocity distribution has not received as much attention. It is shown that the method which neglects the beam-velocity distribution reconstructs electron densities lower than the true values by a factor of ∼2 in the density range up to ∼1×1013 cm-3, while the procedure which takes into account the velocity distribution yields true density profiles in the same density range. Some results of the beam probe mounted in the Heliotron-E device are also described, and good agreement with Langmuir probe measurements is found.
A Study on the Vacuum and Extreme Ultraviolet Emissions from Ionic Rare-Gas-Lithium and -Sodium Molecules by Ab Initio Calculation
Authors: Xing Da , Ken-ichi Ueda Ken-ichi Ueda , Hiroshi Takuma Hiroshi Takuma
Published: February 2005

Ab initio calculations for the electronic states of ionic excimer molecules consisting of rare gases (Rg=Ne, Ar, Kr and Xe) and alkali metals (A=Li and Na) are presented. The calculations include the ground 11Σ+ states and the first-excited 21Σ+ states, which correspond to Rg(1S)+A+(1S) and Rg+(2P)+A(2S) separated limits, respectively. The 11Σ+ states are weakly bound with the calculated binding energies of D
e=0.03-0.34 eV. The 11Σ+ states have potential wells of 0.33-0.98 eV depth. The Franck-Condon factors (FCF's) of the 21Σ+→11Σ+ transitions were computed The emissions from the 21Σ+'s (v′=0) to the higher v′′$ l
e
v
e
l
s (a
b
o
u
t
v$′′=10$) o
f
t
h
e $11Σ+$ h
a
v
e
t
h
e
l
a
r
g
e
s
t
r
e
l
a
t
i
v
e
t
r
a
n
s
i
t
i
o
n
p
r
o
b
a
b
i
l
i
t
i
e
s, w
h
i
c
h
a
r
e
p
r
o
m
i
s
i
n
g
f
o
r
l
a
s
i
n
g
i
n
t
h
e
v
a
c
u
u
m
a
n
d
e
x
t
r
e
m
e
u
l
t
r
a
v
i
o
l
e
t (V
U
V
a
n
d
X
U
V) s
p
e
c
t
r
a
l
r
a
n
g
e
s.
Preparation of TiN Films by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition
Authors: Akahori Takashi , Tanihara Akira , Tano Masashi
Published: February 2005

TiN film is used in the ultra large scale integrated circuit (ULSI) process as a diffusion barrier. Conventional TiN films are deposited by reactive sputtering or by rapid thermal nitridation (RTN) of sputtered titanium layers. Our research group has developed a new ECR (electron cyclotron resonance) plasma CVD (chemical vapor deposition) system capable of depositing metal films. By using this system, TiN films were prepared using TiCl4 and N2 as material gases. It is proven that the films have many advantages: low resistivity, low stress, high barrier property, thick deposition on the bottom of the high aspect ratio's hole and low chlorine concentration in comparison with LPCVD (low pressure chemical vapor deposition) TiN film.
Chemical Stability of HF-Treated Si(111) Surfaces
Authors: Yasaka Tatsuhiro , Kanda Kozo , Sawara Kenichi , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: February 2005

Growth kinetics of native oxide on Si(111) surfaces treated in pH-modified buffered HF (BHF) solutions has been systematically studied by angle-resolved X-ray photoelectron spectroscopy. A BHF-etched (pH=5.3) Si(111) surface has no Si-F bonds and dose not oxidize for 300 min in clean room air. FT-IR-attenuated total reflection (ATR) measurements of Si-H bonds existing on the BHF-treated Si(111) surface have revealed that the surface is nearly step-free and atomically flat. This explains the chemical stability of the Si(111) surface.
Atomic Structure of Hydrogen-Terminated Si(111) Surfaces by Hydrofluoric Acid Treatments
Authors: Morita Yukinori , Kazushi Miki Kazushi Miki , Hiroshi Tokumoto Hiroshi Tokumoto
Published: February 2005

Characterization of “ultra-clean” Si(111) surfaces has been made with atomic-scale resolution by means of scanning tunneling microscopy (STM). The STM images on the flat part of the hydrogen-(H-)terminated Si(111) surface prepared by dipping into the dilute (1%) HF solution exhibit regular dots with threefold symmetry, the distance of 2.2 Å and the corrugation amplitude of 0.5 Å. The origin of these dots is ascribed to the H-related states of the trihydride phase (SiH3): the surface dangling bonds are terminated by the SiH3 radicals which are rotated by 30° from the ideal configuration. In contrast, on the surface prepared by repeating boiling in hot water following 1% HF dipping, we obtain regular dots with threefold symmetry, the distance of 3.8 Å and the corrugation amplitude of less than 0.1 Å. These originate from the H-related states of the monohydride phase (SiH): a single H atom terminates each surface bond by locating on the top site of the surface Si atom.
Interaction of Pd with Strained Layers of Si1-xGex Epitaxially Grown on Si(100)
Authors: Buxbaum A. , Eizenberg M. , Raizman A. , Schäffler F.
Published: February 2005

This work describes the interaction of Pd with MBE grown strained epitxial layers of Si1-x
Ge
x
on Si(100), at low and at high temperatures (250°C and 550°C). Pd was deposited to a thickness of 1700 Å, on the Si1-x
Ge
x
/Si(100) layers with thicknesses of 3300 Å and 2300 Å, and with a Ge contents of x=0.09 and 0.18, respectively. Samples were annealed at temperatures ranging from 250 to 550°C. The reaction products were investigated by Transmission Electron Microscopy, Energy Dispersive Spectroscopy, X-ray dlffraction and Auger Electron Spectroscopy. Strain in the Si1-x
Ge
x
layers was measured by Double Crystal X-ray Diffractometry. Diodes were prepared on n-type substrates, and were characterized by current-voltage techniques. The low temperature interaction is characterized by uniform incorporation of Si and Ge in the Pd2Si1-y
Ge
y
compound (textured on the Si1-x
Ge
x
substrate), and at high temperatures a Ge rich double layer strcucture formed, accompanied by strain relaxation of the Si1-x
Ge
x
layer. The measured Schottky barrier heights were φb=0.67 and 0.65 for x=0.09 and x=0.18, respectively.
Role of SiN Bond Formed by N2O-Oxynitridation for Improving Dielectric Properties of Ultrathin SiO2 Films
Authors: Yasuda Makoto , Fukuda Hisashi , Toshiyuki Iwabuchi Toshiyuki Iwabuchi , Seigo Ohno Seigo Ohno
Published: February 2005

Dielectric and physical properties of N2O-oxynitrided (RTON) ultrathin (5-10 nm) SiO2 films formed by in situ multiple rapid thermal processing have been investigated. In high-field stressing under positive and negative polarity biases, the RTON SiO2 films showed a much lower electron-trap generation rate, a lower field-induced leakage current and a higher charge-to-breakdown value, as compared to those of pure SiO2 and rapid thermally NH3-nitrided (RTN) SiO2 films. Fourier transform-infrared reflection attenuated total reflectance (FT-IR ATR) and X-ray photoelectron spectroscopy (XPS) results showed that strong Si-N bonds are formed at the SiO2/Si interface by RTON, whereas a large number of N-H and Si-H bonds, which act as electron traps, are also generated by RTN.
Simulations of the Current and Temperature Dependence of Liquid Metal Ion Source Energy Distributions
Authors: Richard Hornsey Richard Hornsey
Published: February 2005

Of great importance to the study and application of liquid metal ion sources (LMIS) are the energy distributions of the emitted ions and their variations with source parameters. Excellent data now exist for a wide range of operating conditions but the understanding of energy distributions remains incomplete. The present paper aims to demonstrate that high frequency oscillations in the position of the ion-emitting feature (assumed here to be a jet-like cusp) can give rise to distortions of the energy distribution curves. Such distortions are observed experimentally at high temperatures and currents. Characterisation of the jet oscillations is made in terms of droplet emission from the tip; other parameters are derived from a semi-impirical approach. Energy distribution shapes are determined by the waveform of the oscillation; complete results are presented for a simplified waveform and the effects of other waveform characteristics are discussed.
Low Temperature Poly-Si TFTs Using Solid Phase Crystallization of Very Thin Films and an Electron Cyclotron Resonance Chemical Vapor Deposition Gate Insulator
Authors: Little Thomas W. , Takahara Ken-ichi , Koike Hideki , Nakazawa Takashi , Ichio Yudasaka Ichio Yudasaka , Hiroyuki Ohshima Hiroyuki Ohshima
Published: February 2005

Low temperature (T≦600°C) polycrystalline silicon thin film transistors (poly-Si TFTs) have been fabricated by solid phase crystallization (SPC) of amorphous silicon (a-Si) films deposited by low pressure chemical vapor deposition (LPCVD). These TFTs are distinguished by the very thin nature of the channel Si layer (25 nm) and the use of an SiO2 gate insulator deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD). The present process eliminates the need for hydrogenation and produces mobilities greater than 20 cm2/V·s and on/off current ratios greater than 107.
Display Performance Improvement of Thin-Film Diode Liquid-Crystal Display by a Low-Temperature Anodizing Method
Authors: Keiko Sunohara Keiko Sunohara , Hiroshi Morita Hiroshi Morita
Published: February 2005

The thin-film diode liquid-crystal display (TFD-LCD) with low-temperature anodic-oxidation film (LTAOF) appears to achieve display performance improvements. From the experimental results, for the TFD element with LTAOF, the steepness of current-voltage characteristics (β) is larger and its capacitance is smaller than that for conventional TFD fabricated by room-temperature anodic oxidation. The authors have paid special attention to the oxide layer state. Using the results of several measurements and analyses, this paper indicates the reason why TFD-LCD with LTAOF shows good display performance.
Surface States for the GaAs(001) Surfaces Observed by Photoemission Yield Spectroscopy
Authors: Hirose Kazuyuki , Noguchi Takao , Uchiyama Akihiko , Uda Masayuki
Published: February 2005

The energy distributions of the occupied surface states of GaAs (001) surfaces are measured using photoemission yield spectroscopy. The surfaces are prepared by different kinds of techniques, including molecular beam epitaxy, As decapping, and chemical etching. The surface states are found to change in both distribution and density depending on the surface preparation techniques. The origins of the surface states are discussed in terms of surface atomic structures for the atomically clean surfaces. A great reduction by about one order of magnitude in the density of the surface states is revealed for the surface covered with native oxide compared with the other atomically clean surfaces: the surface state electron density is estimated to be about 3×1013 cm-2 for the latter, and ∼1012 cm-2 for the former.
Multicusp Type Electron Cyclotron Resonance Ion Source for Plasma Processing
Authors: Amemiya Hiroshi , Ishii Shigeyuki , Shigueoka Yoshyuki
Published: February 2005

A multi-cusp type ECR (electron cyclotron resonance) ion source is built with use of SmCo magnets and 2.45 GHz-TE11 circular mode microwave. The ion source is operated at pressures from 10-4 to 10-3 Torr with the input microwave power from 100 to 400 W. In hydrogen, the current density of H+ is higher than those of H2
+ and H3
+. The dependence of the fraction of each ion species on the power and pressure is measured and explained by rate equations.
The source is operated also in other gases. Mass spectra in He, N2, O2, Ar and CH4 are shown together with the pressure and power dependences. Multicharged state of up to 3 has been obtained.
Migration-Enhanced Epitaxy of InP Using Polycrystalline InP as Phosphorus Source
Authors: Bing-Xiong Yang Bing-Xiong Yang , Hideki Hasegawa Hideki Hasegawa
Published: February 2005

InP was successfully grown by the migration-enhanced epitaxy (MEE) mode using polycrystalline InP as the phosphorus source in a conventional GaAs-type molecular beam epitaxy (MBE) chamber. A long and persistent reflection high-energy electron diffraction (RHEED) oscillation was observed. (2×4) RHEED patterns were observed in both In-supply and P2-supply periods, being different from the GaAs MEE growth. Compared with the conventional MBE, the MEE growth afforded epitaxial layers of better surface morphology and greatly improved photoluminescence properties.
Complex Susceptibility of Bi2Sr2Ca1-xYxCu2Oy from Citrate Sol-Gel Precursors
Authors: Mazaki Hiromasa , Kakihana Masato , Hiroshi Yasuoka Hiroshi Yasuoka
Published: February 2005

In order to examine the dependence of the superconducting property of the double Cu-O layer system on the hole concentration, we measured the superconducting transition of Bi2Sr2Ca1-x
Y
x
Cu2O
y
(0≦x≦0.4) compounds in terms of complex susceptibility, χ=χ′-iχ′′. The samples were synthesized by a citrate sol-gel precursor technique. The main advantages of this method are the shorter reaction time, the elimination of some steps such as centrifugation, and a fine control of pH. X-ray diffraction analysis showed that each sample has a single phase, although χ for x=0.1 indicates the existence of different superconducting phases. It has been revealed that the superconducting transition temperature T
c apparently depends on the hole concentration, and the highest T
c (95.2 K) was achieved for around x=0.1. The profiles of χ for five samples with different values of x are discussed.
Preparation of PbTiO3 Thin Films by Ion- and Photoassisted Evaporation
Authors: Hayashi Shigenori , Kenji Iijima Kenji Iijima , Takashi Hirao Takashi Hirao
Published: February 2005

PbTiO3 films were grown on MgO substrates by the recently developed ion- and photoassisted evaporation technique. Pb and Ti were evaporated from electron-beam-heated metal sources under the irradiation of an oxygen ion beam and excimer laser beam for the ion activation and for the photoactivation, respectively. Crystal structure of the films was significantly affected by ion energy, ion current, laser pulse energy and repetition rate. The substrate temperature required for in-situ preparation of perovskite PbTiO3 could be lowered to 450°C by ion-assisted evaporation and to room temperature by ion- and photoassisted evaporation.
Hysteresis Loops and Microstructures of Fe/Ag Multilayer Films
Authors: Haga Yumiko , Nakamura Yoshio , Akira Sugawara Akira Sugawara , Osamu Nittono Osamu Nittono
Published: February 2005

The relationship between magnetic properties and microstructures in the Fe/Ag system has been investigate. Fe/Ag multilayer films with a thickness ratio of 1/10=Fe/Ag were prepared by a double-facing-target-type dc sputtering apparatus. The M-H loops measured using a vibrating sample magnetometer showed that they had some uniaxial anisotropies in the film plane, and some steps were observed on the loops measured for the average easy axis, especially when the Fe layer thickness was larger than 6.5 nm. It was found that the number of steps was equal to that of inserted Fe layers. Microstructures of the films were investigated by X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy. The films were composed of alternate stacking of Fe{110} and Ag{111} planes and constructed with many columns growing along the stacking direction. The origin of steps on the M-H loops is discussed on the basis of experimental results.
InP/InGaAs Double Heterojunction Bipolar Transistors Grown on Si
Authors: Makimoto Toshiki , Kurishima Kenji , Kobayashi Takashi , Ishibashi Tadao
Published: February 2005

The first InP/InGaAs double heterojunction bipolar transistors on Si substrates were grown by metalorganic chemical vapor deposition. The transistor with an InP buffer layer thickness of 4 µm exhibited high current gains of more than 250 and an ideality factor of 1.3. (The base doping concentration and its thickness were 1.5×1019 cm-3 and 700 Å, respectively.) The characteristics of the DHBT on Si with the 4-µm buffer layer are comparable to those of transistors on InP substrates.
Sub-Quarter-Micron Gate Fabrication Process Using Phase-Shifting Mask for Microwave GaAs Devices
Authors: Inokuchi Kazuyuki , Saito Tadashi , Jinbo Hideyuki , Yoshio Yamashita Yoshio Yamashita , Yoshiaki Sano Yoshiaki Sano
Published: February 2005

A phase-shifting mask technique using an i-line stepper was applied to the gate formation process of AlGaAs/GaAs high electron mobility transistors (HEMTs). To obtain a fine gate pattern of less than a quarter micron, the phase-shifter edge-line mask, which has the highest resolution and wide focus margin for an isolated pattern, was used and the double exposure process was developed to form a real gate pattern. The controllable gate length was in the range of 0.50-0.15 µm. By using this technique, 0.18 µm-gate HEMTs with good and uniform microwave performances in a 3-inch wafer were obtained. This technique has great advantages for applications to microwave GaAs devices and ultrahigh-speed GaAs LSIs.
A GaAs Floated Electron Channel Field Effect Transistor (FECFET) Fabricated by Selective Metal Organic Chemical Vapor Deposition
Authors: Kim Chang-Tae , Chang-Hee Hong Chang-Hee Hong , Young-Se Kwon Young-Se Kwon
Published: February 2005

We have proposed and fabricated a new GaAs FET with very short channel, which we call Floated Electron Channel Field Effect Transistor (FECFET), using the Selective Metal Organic Chemical Vapor Deposition (SMOCVD) technique. The channel length of the proposed device is reduced by placing the channel layer on the top of the triangular void. The formation of the triangular void is well characterized by both the growth parameters of the SMOCVD and the mask orientation. The maximum extrinsic transconductance of 260 mS/mm is obtained for the gate length larger than 2 µm and the measured source resistance is 0.25 Ω·mm. It is also observed that the measured transconductance is almost independent of the gate length when the fabricated gate has a length between 2.0 µm and 4.0 µm. The effective channel length is mainly determined by the short distance between two n+ layers for source and drain rather than the gate length. This device structure is suitable for low noise FET and for the simple realization of direct coupled FET logic inverter.
Complementary InAs n-Channel and GaSb p-Channel Quantum Well Heterojunction Field-Effect Transistors
Authors: Yoh Kanji , Taniguchi Hiroaki , Kazumasa Kiyomi Kazumasa Kiyomi , Masataka Inoue Masataka Inoue
Published: February 2005

We report on the fabrication and characterization of vertically integrated InAs n-channel Heterojunction Field-Effect Transistors (HFETs) and GaSb p-channel HFETs based on a (Al0.5Ga0.5)Sb/InAs/(Al0.5Ga0.5)Sb/GaSb/(Al0.5Ga0.5)Sb double quantum well heterostructure grown by molecular beam epitaxy (MBE). The operation of both p- and n-channel HFETs fabricated on the double quantum well heterostructure is demonstrated for the first time. Vertically integrated 1 µm-gate-length GaSb p-channel HFET and 1.2 µm-gate-length InAs n-channel HFETs showed decent I-V characteristics with maximum transconductances of 19 mS/mm and 88 mS/mm at 77 K, respectively.
Accumulation-Mode GaAlAs/GaAs Bipolar Transistor
Authors: Matsumoto Kazuhiko , Ishii Masami , Morozumi Hidehiro , Imai Seiji , Sakamoto Kunuhiro , Hayashi Yutaka , Liu William , Costa Damian , Ma Tony , Massengale Allan , Harris James S.
Published: February 2005

The accumulation-mode bipolar transistor is proposed and investigated for the first time. The transistor uses the two-dimensional hole gas (2DHG) as an ultrathin base layer, which is accumulated at the AlAs barrier-p
- collector interface. The transistor shows the common-emitter current gain of ∼30. The theoretical results reveal that by adopting the p
- collector rather than the n
- collector, and with the higher impurity concentration, the carrier concentration of the 2DHG base, the turn-on emitter-base bias, and the punch-through base-collector bias are improved drastically.
Vibration of Beryllium Foil Window Caused by Plasma Particle Bombardment in Plasma Focus X-Ray Source
Authors: Sato Toshihiko , Ochiai Isao , Yasuo Kato Yasuo Kato , Seiichi Murayama Seiichi Murayama
Published: February 2005

The effect of plasma particle bombardment on beryllium foil windows was investigated by the displacement measurement of the window foil. It was experimentally verified that the beryllium foil began to vibrate after a shot of plasma focus discharge. It was also verified by the displacement measurement that the particle bombardment caused a thermal expansion of the foil. All these dynamic effects of particle bombardment suggested that fatigue fracture of the foil played an important role in the process of the beryllium foil destruction.
Wigner Function Formulation of Quantum Transport in Electron Waveguides and Its Application
Authors: Tsuchiya Hideaki , Matsuto Ogawa Matsuto Ogawa , Tanroku Miyoshi Tanroku Miyoshi
Published: February 2005

A Wigner function model is successfully formulated for the first time to simulate the quantum mechanical transport in an ideal electron waveguide. The temperature dependence of the two-terminal conductance of a perfect electron waveguide, and the static and dynamic behavior of an electron waveguide with a potential barrier (well) are presented. For an abrupt switching to a potential well, an oscillatory current transient is observed due to the resonance of an electron wave.
600 nm-Range GaInP/AlInP Multi-Quantum-Well (MQW) Lasers Grown on Misorientation Substrates by Gas Source Molecular Beam Epitaxy (GS-MBE)
Authors: Kikuchi Akihiko , Katsumi Kishino Katsumi Kishino , Yawara Kaneko Yawara Kaneko
Published: February 2005

The 600 nm-range GaInP/AlInP multi-quantum-well (MQW) lasers grown by gas-source molecular beam epitaxy were investigated. Nonradiative recombination at heterointerfaces was drastically reduced by use of superlattice cladding (SLC) layers and 15° misoriented substrates (from (100) toward the [011] direction), resulting in increments of PL peak intensities from active layers by factors of 20 and 2, respectively. In addition to these effects, we changed the well numbers optimizing at three. As a result, a very low threshold current density (J
th) of 2.0 kA/cm2 was obtained at a lasing wavelength of 629nm, without strain effects. Finally, experimental rapid deterioration of J
th and characteristic temperatures by shortening of the wavelengths was explained by leakage current components over the heterobarrier.
Integration of PIN and Vertical Junction Field Effect Transistor for Photodetector Optoelectronic Integrated Circuit
Authors: Myeong-Kook Gong Myeong-Kook Gong , Young-Se Kwon Young-Se Kwon
Published: February 2005

The integration of a PIN photodiode and a vertical junction field effect transistor (VJFET) is useful for optoelectronic integrated circuit (OEIC) since the structure is compact and has potentially high power and high speed capabilities. A GaAs VJFET with the gate connected to PIN was fabricated. The fabricated PIN has a low leakage current, below 50 nA at 10 V bias. Two step atmospheric pressure metalorganic chemical vapor deposition (AP MOCVD) was used and the second step epitaxial layers were selectively grown using silicon dioxide (SiO2) mask. The gate p-layer has a tungsten (W) layer on it and was doped by carbon to prevent autodoping during the second step epitaxy. This VJFET has an improved current-voltage characteristics than the one without W on p-gate layer.
Fabrication and Noise Properties of NbN Nanobridge dc Superconducting QUantum Interference Devices (SQUIDs)
Authors: Irie Akinobu , Abe Hiroya , Michal Hatle Michal Hatle , Katsuyoshi Hamasaki Katsuyoshi Hamasaki
Published: February 2005

We have fabricated two types of NbN nanobridge dc Superconducting QUantum Interference Devices (SQUIDs). From the analyses of the response to magnetic field, it is found that the current-phase relationship for the planar-type nanobridge and the nanobridge fabricated by field evaporation is close to sinusoidal. For V\gtrsim720 µV, The spectral densities of the voltage noise show linear dependence on the voltage for the SQUIDs with nanobridges whose length is about the superconducting coherence length of NbN. The SQUIDs with nanobridges with lengths of several times the NbN coherence length exhibit parabolic voltage dependence.
Properties of the Nb Thin-Film Nanobridges Prepared by Nanometer Fabrication Process
Authors: Harada Yuichi , Hirose Nobumitsu , Uzawa Yoshinori , Matsuo Sekine Matsuo Sekine
Published: February 2005

We describe the properties of Nb thin-film nanobridges fabricated by means of our original nanometer-scale process. Our original nanofabrication techniques include the synthesis of a new electron beam (EB) resist and the use of CBrF3 as an etchant for reactive ion etching (RIE). Fabricated nanobridges have high sensitivity of radiation and high reliability. It is observed that the properties of nanobridges can be changed by varying the bridge length and its thickness. We have also fabricated the series arrays and observed that they operate coherently.
A Quantum Flux Parametron (QFP) 12-Bit Shift Register Capable of Stable Microwave Frequency Operation
Authors: Casas Juan , Kamikawai Ryotaro , Nobuo Miyamoto Nobuo Miyamoto , Eiichi Goto Eiichi Goto
Published: February 2005

A 12-bit shift register employing the quantum flux parametron (QFP) as its basic element is presented. The 12-bit shift register operates at frequencies from dc up to 4.24 GHz with an on-chip total power consumption below 10 nW. Such a low power consumption is possible to obtain because (1) the QFP has very little power dissipation and (2) the clock lines do not dissipate power. The clock current is applied as a standing wave and is distributed by inductive division. The output waveform has been sampled in the time domain at a clock frequency of 2.4 GHz in spite of the low output signal amplitude (about 10 µV) and of the large crosstalk with the clock frequency. The 12-bit shift register is capable of stable operation, demonstrating that at least 1015 error-free operations per QFP are possible.
Magnetic Analysis of Plasma Configuration in Tokamak Experiment Using Boundary Element Method
Authors: Takeuchi Kazuhiro , Abe Mitsushi , Hideshi Fukumoto Hideshi Fukumoto , Michio Otsuka Michio Otsuka
Published: February 2005

A method of magnetic analysis has been developed for experimental study of tokamak plasma configuration. The boundary element method has been applied to the determination of the magnetic flux distribution in a region bounded by magnetic sensors. The plasma cross-sectional shape is obtained without the difficulties that arise in the evaluation of the effects of the iron core of the transformer or of the eddy currents if they are excluded from the poloidal region encircled by magnetic sensors. The accuracy and validity of this method is checked by means of a comparison with numerically obtained MHD equilibria. The results have shown that the location of the plasma surface positions have been identified with an error of several percent of the plasma minor radius. This method has been applied to the analysis of the HT-2 experiment. Fairly good agreement is obtained between the magnetic analysis and limiter potential measurements.
Thermal Annealing of Radicals in Aragonitic CaCO3 and CaHPO4·2H2O
Authors: Toshikatsu Miki Toshikatsu Miki , Ayako Kai Ayako Kai
Published: February 2005

High-temperature annealing of radicals in aragonitic CaCO3 and in CaHPO4·2H2O has been studied by electron spin resonance (ESR), thermometric analyses (DTA and TGA) and thermally stimulated gas release (TSGR). An isotropic ESR signal at g=2.0007 is detected in coral and irradiated CaHPO4·2H2O. The signal in aragonitic coral is annealed out at 150-210°C, but the same signal in CaHPO4·2H2O fades out at 100-140°C. The signal annihilation is accompanied by water release from the specimens. The formation yield of the g=2.0007 signal by irradiation is reduced by sample preheating. The experimental results indicate that isotropic CO2
- radicals responsible for the g=2.0007 signal are closely associated with the crystal water in aragonitic CaCO3 and in CaHPO4·2H2O. Some isotropic CO2
- radicals may be associated with CO2
- ions isolated by surrounding water molecules.
Microfabrication of Dielectric Multilayer Reflector by Reactive Ion Etching and Characterization of Induced Wafer Damage
Authors: Matsutani Akihiro , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

A reactive ion etching (RIE) system has been introduced to fabricate a tiny structure of dielectric multilayer reflector for a microcavity surface emitting laser. Some etching characteristics of dielectric materials (Si, SiO2 and TiO2) with CF4 gas have been investigated using RIE. A 7-pair SiO2/TiO2 circular multilayer reflector with a diameter of 5 µm is successfully fabricated. In addition, the induced damage of the GaAs wafer was evaluated by PL measurement.
Microstructure of YBa2Cu3O7-x Superconductor Synthesized with Y2BaCuO5, BaCuO2 and CuO
Authors: Lee Soo Young , Ko Jae Woong , Hai Doo Kim Hai Doo Kim , Hyung Sik Chung Hyung Sik Chung
Published: February 2005

YBa2Cu3O7-x
(123) superconductor was synthesized with pre-synthesized Y2BaCuO5 (211), BaCuO2 and CuO powder. The development of microstructures in this system was studied in detail. Highly densified and well aligned 123 phase can be obtained by a slow cooling heat-treatment and a transient liquid phase sinterting.
The presence of transient liquid phase provides a large driving force for the formation of long plate shape 123 grains. Finely and homogeneously distributed 211 particles are trapped in 123 phase. A well-aligned grain structure of 123 phase was produced by the applying of a slow cooling heat-treatment to this system.
A Study on the Behavior of SiO2 Film Precursors with Trench Deposition Method for SiH4/O2 Low Pressure Chemical Vapor Deposition
Authors: Kawahara Takaaki , Akimasa Yuuki Akimasa Yuuki , Yasuji Matsui Yasuji Matsui
Published: February 2005

Silicon dioxide thin films have been deposited from silane and oxygen at 540 K and 3.5 Torr in a cold-wall reactor. The trench deposition method is applied to clarify the behavior of film precursors for the SiO2 deposition. It has been found that surface reactions scarcely contribute to the deposition in the present conditions, and that the overall sticking probability of the film precursor changes significantly with the substrate temperature. This phenomenon is shown to be satisfactorily explained by the model that the precursors formed by gaseous reactions consist of several kind of radicals with different sticking probabilities. It is also shown that the decrease in the deposition rate for O2-excess region corresponds to the radical concentration in the gasphase.
Study of CuInSe2 Formation Kinetics in the Selenization Process by Raman Spectroscopy
Authors: Yamanaka Satoshi , Tanda Masayuki , Nakada Nobuyuki , Yamada Akira , Makoto Konagai Makoto Konagai , Kiyoshi Takahashi Kiyoshi Takahashi
Published: February 2005

Formation kinetics of polycrystalline CuInSe2 films in selenization of Cu/In/Se stacked layers was studied using Raman spectroscopy. Raman spectra of the films clearly show a structural change of the film at elevated temperatures. It is concluded that Cu is selenized preferentially at low temperatures around 200°C and that the CuInSe2 phase is formed at temperatures above 250°C.
Two-Dimensional Growth of GaP on Si Substrates under High V/III Ratio by Metal Organic Vapor Phase Epitaxy
Authors: Imaizumi Mitsuru , Saka Takashi , Jimbo Takashi , Tetsuo Soga Tetsuo Soga , Masayoshi Umeno Masayoshi Umeno
Published: February 2005

Direct heteroepitaxial growth of GaP layers on Si substrates by metal organic vapor phase epitaxy (MOVPE) has been studied. The effects of growth temperature and the V/III ratio on the layers were investigated. Hillocks appeared when the growth temperature was lower than 850°C. It was clarified that the growth is two-dimensional when the V/III ratio is higher than 600. Once the two-dimensional growth is realized at the initial stage, the subsequent growth is easily attained under the condition of low V/III ratios. The crosshatch pattern was observed on the surface. The EBIC plan images show the dark lines corresponding to crosshatches and dark spots. The dark spot density (DSD) is less than 3×105 cm-2.
Ammonium Sulfide Passivation for AlGaAs/GaAs Buried Heterostructure Laser Fabrication Process
Authors: Tamanuki Takemasa , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

We have introduced ammonium sulfide ((NH4)2S
x
/(NH4)2S) treatment to reduce the surface recombination in the regrowth process of an AlGaAs/GaAs buried heterostructure (BH) laser by MOCVD. The (NH4)2S
x
-treated BH lasers showed much lower threshold current than BH lasers without the chemical passivation. This fabrication technology is expected to be very effective for the realization of ultralow-threshold micro-cavity lasers with a few-micron or submicron cavity structure.
Effect of Grain Growth of Hot-Pressed Magnesium Fluoride on Optical Transmittance
Authors: Chang Chen-Shen , Yang Min-Hsiung Hon
Published: February 2005

Hot-pressing powdered magnesium fluoride, under the conditions of an air, a temperature varying within the range from 510 to 690°C, a pressure of 40,000 psi, and a holding time under pressure of 30 minutes, resulted in a polycrystalline plate or shape with high in-line optical transmittance. The effect of grain growth of the sample on the optical transmittance in the window region is discussed. The positions of the transmittance cutoff for long wavelength and short wavelength are investigated. It is proposed that the shift of short-wavelength transmittance cutoff toward longer wavelength is caused primarily by the pore growth that is associated indirectly with the grain growth, that the shift of the long wavelength transmittance cutoff is almost independent of the microstructure, and that the shifts of both long wavelength and short wavelength are very dependent on the sample thickness. The importance in optical transmittance of the anisotropic grain compared with the pore might become significant when the thickness of a pair of samples is considerably reduced.
Estimation of the Donor Concentration in ZnSe from the Emission Related to Donor Bound Excitons
Authors: Isshiki Minoru , Masumoto Katashi , Uchida Wakio , Satoh Shiro
Published: February 2005

The relation between the donor concentration (N
D) and the total emission intensity related to the donor bound excitons has been ascertained using doped and nondoped high-purity ZnSe single crystals. Two different relations were obtained for as-grown and Zn-dipped crystals. These relations are available for reference curves to estimate the value of N
D in ZnSe single crystals.
Influence of Thermally Created Sulfur Vacancies on Sublimation of Cadmium Sulfide Crystals
Authors: Jiro Nishimura Jiro Nishimura
Published: February 2005

Cadmium sulfide vapor pressure measured by means of the glass membrane manometer method is discussed. The {log10
P, T
-1} curve consists of two straight lines corresponding to the temperature ranges below and above a critical temperature T
c (=740 K). The sublimation enthalpy obtained from the straight line below T
c was 76.4 k·cal/mol, which agrees well with the enthalpy of sublimation of the well-known reaction, CdS(s)=Cd(g)+(1/2)S2(g). As for sublimation above T
c, it is concluded that, in addition to the said reaction, another reaction, CdS(s)=CdS1-x
(s)+(x/2)S2(g), occurs which causes sublimation suppression, and that the activation energy necessary to create an excess of Cd (a sulfur vacancy) in a CdS crystal is 3.19 k·cal/mol or 0.138 eV.
Pyrolysis Behavior and Themostability of Branched-Chain and Hydroxylated Straight-Chain Fatty Acid Moleculars
Authors: Toshiaki Ushikusa Toshiaki Ushikusa
Published: February 2005

The weight loss behaviors and thermostability of four iso and anteiso branched-chain fatty acids, and four hydroxylated straight-chain saturated fatty acids in air and nitrogen flows were studied by thermogravimetry (TG) and derivative thermogravimetry (DTG). The branched acids showed a simple weight loss pattern in their TG and DTG curves in both air and nitrogen flows, whereas a more complicated pattern was observed for the hydroxy fatty acids. The TG and DTG curves of the fatty acids shifted to the higher-temperature side with an increase in the number of carbon atoms. The weight loss was found to be caused mainly by evaporation accompanied with a small degree of decomposition. Thermostability of the hydroxy fatty acids evaluated with initial temperature of weight loss was shown to be superior to that of the straight- and branced-chain fatty acids.
A Collection Method for Ultrafine Particles Produced by the Gas Evaporation Technique
Authors: Kaito Chihiro , Yoshimura Yukio , Yoshio Saito Yoshio Saito
Published: February 2005

A method of collecting ultrafine particles by gas flow has been introduced. Aluminium particles were collected in order to check the flow gas effect on the morphology. The growth conditions of tetrataenite particles have been elucidated experimentally.
Change of Structure and Electrical Properties of FeSi2 Thin Film during Annealing
Authors: Komabayashi Masashi , Ido Ken-ichi Hijikata
Published: February 2005

Changes of structure and electrical properties of FeSi2 thin film by annealing at 380-600°C were studied and the crystallization process of the film was discussed. As a result of annealing, transformation from an amorphous phase to FeSi2 crystal occurred at 380-420°C. FeSi2 crystalline in the film was imperfect and the number of defects decreased with increasing annealing temperature. The electrical resistivity, Seebeck coefficient and activation energy associated with acceptor levels increased with increasing annealing temperature throughout the temperature region. These changes in the electrical properties by annealing were explained by the decrease in the number of defects on annealing. Carrier mobilities in the annealed films at various temperatures were deduced from the results of activation energy measurement.
Emissive Probe Study of CF4/H2 Etching Plasma
Authors: Shindo Haruo , Masayoshi Konishi Masayoshi Konishi , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

A new method using an emissive probe was applied to measurement of the electron temperature in a CF4/H2 etching plasma in which the deposition of CF
x
polymer occurred. The experiment firstly showed that the measurement by our new method was never deteriorated by the deposition on the probe surface and was free from the influence of the deposition-induced plasma drift. The electron temperature thus measured rapidly decreased as the content of H2 was increased. It was further shown that the electron temperature obtained by the emissive probe method was very consistent with that spectroscopically determined using the Hα and Hβ line intensity ratio.
Measurement of Electrical Characteristics of Stored Be+ Ions in a Penning Trap
Authors: Hidetsuka Imajo Hidetsuka Imajo , Shinji Urabe Shinji Urabe
Published: February 2005

A Penning trap is designed for utilization in ultrahigh-resolution spectroscopy and atomic physics. The stored Be+ ions in this trap are detected electrically by the rf absorption method. The total number, axial frequency and storage time of the stored ions are measured. The axial frequency of the stored ions is theoretically estimated by considering the space charge effect and is compared with the measurements.
keV Ion-Beam-Exposed Poly(methylisopropenylketone) and Poly(phenylisopropenylketone)*
Authors: Wen-an Loong Wen-an Loong , Nien-tsu Peng Nien-tsu Peng
Published: February 2005

The exposure characteristics of poly(methylisopropenylketone) (PMIPK) and poly(phenylisopropenylketone) (PPIPK) exposed to 40 and 80 keV H+ and B+ ion beams have been studied. It is found that the electron-rich phenyl group in PPIPK has increased stopping power for the bigger B+ ion, but not for the smaller H+ ion. For the same reason, the main chain scissioning of PPIPK is slower than that of PMIPK when they are exposed to B+, but not to H+, under the same exposure conditions. Linear relationships are found with simulation parameter A which stands for exposure efficiency of the ion beam as a function of exposure doses (keV×ion fluence) for a specific ion-exposed polymer within the used energy range.
Analysis of Sputtered Neutrals by Nonresonant Multiphoton Ionization I. Development of Laser Ion Counting System with a Simple Time-of-Flight Measurement
Authors: Eizoh Kawatoh Eizoh Kawatoh , Ryuichi Shimizu Ryuichi Shimizu
Published: February 2005

A simple time-of-flight, pulse-counting system is introduced to a sputtered neutral analysis by a nonresonant multiphoton ionization technique. The system consists of an ion acceleration assembly, a flight tube, a microchannel plate detector and pulse-counting electronics. A direct counting of detected photoions on each laser shot provided a new capability of comparing different elements with no detection efficiency difference.
Modeling Thermal Effects for Simulation of Post Exposure Baking (PEB) Process in Positive Photoresist
Authors: Asai Satoru , Hanyu Isamu , Mitsuji Nunokawa Mitsuji Nunokawa , Masayuki Abe Masayuki Abe
Published: February 2005

We studied the thermal effects in a positive photoresist during post exposure baking (PEB). Infrared analysis and the reduced dissolution rate in the exposed resist suggest that the carboxylic acid is decreased and/or that ECA solvent evaporates. In order to simulate the effects, we assume that the concentration of the alkali-soluble material (carboxylic acid) decreases equivalently. Our model explains PEB and enables its effects to be simulated.
Magnetic Anisotropy of Fe/SiO2 Multilayer Film
Authors: Masakatsu Senda Masakatsu Senda , Yasuhiro Nagai Yasuhiro Nagai
Published: February 2005

This paper investigates the in-plane magnetic anisotropy of Fe/SiO2 multilayer film. Fe/SiO2 film exhibits field-induced uniaxial anisotropy which depends strongly on the Fe and SiO2 layer thickness. Maximum uniaxial anisotropy leads to minimum coercivity. The interfaces between Fe and SiO2 layers deteriorate uniaxial anisotropy. There is no correlation between the anisotropy field and magnetostriction. No in-plane anisotropy of the film stress, crystal orientation, or crystal grain shape is observed in Fe/SiO2 film prepared with an external field. Also, the Fe layer maintains the same atomic state as bulk-Fe. The multilayering effects, such as magnetostatic coupling between Fe layers and small crystal grains, play an important role in making anisotropy dispersions small, and enhancing the uniaxial anisotropy of Fe layers in Fe/SiO2 film.
Metal Organic Chemical Vapor Deposition Growth of GaAs on Si Using GaAs Buffer Layer Grown by an Alternate Gas Flow of Source Materials
Authors: Fujita Kazuhisa , Hiroto Kanao Hiroto Kanao , Yasunari Shiba Yasunari Shiba
Published: February 2005

We tried the atomic layer epitaxy (ALE) growth of GaAs initial layer in a two-step growth of GaAs on Si by a conventional metal organic chemical vapor deposition (MOCVD) system. The etch pit density of GaAs overlayer became smaller than that without this approach. The cross sectional transmission electron microscope (TEM) of this sample indicated that the improvement of crystalline quality of GaAs overlayer was attributed to the smooth interface structure of GaAs/Si due to the layer by layer growth of the buffer layer.