bluuebunny/crossref_metadata_2025 huggingface dataset:
Microdefects Formed in Carbon-Doped CZ Silicon Crystals by Oxygen Precipitation Heat Treatment
Authors: Kanamori Masaru , Tsuya Hideki
Published: November 2005

In order to clarify the role of carbon regarding interstitial oxygen precipitation and secondary defect formation in a CZ silicon crystal, we performed various nucleating preanneals for carbon-doped (intentional) crystals and examined microdefect formation and the perfectness of the denuded zone by selective etching, TEM observation and spreading-resustance measurements following donor formation and angle lapping near the surface. In a high carbon content crystal many anomalies such as etch-pit density reduction, thermal-donor formation at 1000°C and large defect formation below the surface were observed. Carbon atoms acted as oxygen-precipitation nuclei, resulting the generation of a very small precipitate, which induced a low-density secondary defect and partly acted as a high-temperature donor. At an appropriate [O
i]/[C] ratio near the surface, large oxides were formed with secondary defects. The favorable carbon content for gettering site formation during a short time was estimated from these experiments.
A Direct Search Method for Determining Spin Hamiltonian Parameters
Authors: Kobayashi Tadashi
Published: November 2005

A convenient direct-search method for determining spin Hamiltonian parameters is described for the S=1 or 3/2 types of the spin Hamiltonian \mathscrH=β(g

X

H

X

S

X
+g

Y

H

Y

S

Y
+g

Z

H

Z

S

Z
)+D[S

Z

2-S(S+1)/3]+E(S

X

2-S

Y

2). To find the Eulerian angles, by which the principal axis system is related to the crystallographic axis system, a two-circle ESR goniometer with a Wulff's net mounted on the projection plate is used. The ESR analysis of KH2PO4:Cr3+ is detailed as an example.
A CCD Imager on Three Types of P-Wells
Authors: Miyatake Shigehiro , Nagakawa Tadashi , Misawa Kiyotoshi , Kosaza Harumi , Sakamato Shoji , Ogawa Shin-ichi , Fujino Kozo , Yamano Toshiaki , Iikawa Kanpei , Nakai Jun-ichi , Matsui Osamu , Awane Katsunobu
Published: November 2005

A 488×590-elment interline-transfer CCD imager for the 2/3-inch formal is described. It employs three types of p-wells (shallow, medium, and deep) for smearing suppression as well as for blooming suppression. The shallow p-well incorporates the photodiodes and is completely depleted for blooming suppression. The medium one does the CCD shift registers and also is completely depleted for smearing suppression. The deep one does the output circuitry and is not completely depleted for the stable MOS transistor operation. For 10-percent vertical-height illumination, the smear signal was as small as -73 dB of the illumination signal at a wavelength of 550 nm. Furthermore, this imager employs n+-n--p photodiodes to reduce the change of spectral response with a storage of signal charge.
Radical Concentrations and Prompt NO Formation in Hydrocarbon-Air Premixed Flames
Authors: Matusi Yasuji , Yuuki Akimasa
Published: November 2005

Hydroxyl radical concentrations in laminar, premixed CH4-air flat-flames were measured by a conventional absorption method in the flame temperature range T=2200–1700 K. The OH mole fractions in the reaction zone P
OH were found to be insensitive to the flame temperature and the maximum P
OH to be about 6×10-3 at T=2000 K in a stoichiometric flame. The rate constant for the prompt NO formation, CH+N2→HCN+N\dashrightarrow2NO (4), is modified as k
4=1.2 ×1012 exp
(-13600/R
T) by the relation between the amount of prompt NO and the saturation ion current I
s. It is also shown from the measurements of NOx, unburnt hydrocarbons H.C., and I
s, that the chemical kinetics are not significantly influenced by the flame temperature, and NO emission is reduced by reactions among NO, H.C., and N-containing intermediate species in low-temperature flames, even in stoichiometric and fuel-lean mixtures.
Numerical Analysis of the Transport Phenomena in MOCVD Process
Authors: Kusumoto Yoshiro , Hayashi Toshiro , Komiya Souji
Published: November 2005

The transport properties of the convective fluid motion in a MOCVD reactor are investigated using a numerical method. For the purpose of a uniform deposition rate on a substrate with a diameter of 3 inches, a combinatorial optimization was carried out concerning the pressure, the mass-flow rate and the reactor's geometry. Under the optimal condition, a deposition uniformity within ±0.6% is attainable. The results also reveal a variety of flow configurations, depending on the relative magnitudes of the forced and natural convections. When the volumetric velocity of the supplied gas decreases, a recirculating vortex appears on the upstream side of the deposition surface. The numerical results suggest that the appearance of the vortex is governed by F
r/R
e when R
e<R
e
c and by F
r when R
e>R
e
c.
Absorption, Luminescence, and Coloration in Sulfur-Doped KCl and KBr Crystals
Authors: Baba Mamoru , Ikeda Toshio
Published: November 2005

Luminescence emission and coloration due to the photochemical reaction were induced by irradiation into the characteristic absorption bands of KCl-S and KBr-S crystals. As-grown crystals show ultraviolet(uv) luminescence at liquid nitrogen temperature (LNT) on irradiation into the characteristic absorption bands due to precipitates. In quenched crystals, excitation into short-wavelength absorption bands around 4.7∼4.8 eV produces uv and blue emissions at LNT, and coloration due to the formation of F centers and blue emission at room temperature (RT). Excitation into long-wavelength absorption bands around 3.55∼3.60 eV produces red emission both at LNT and RT. The results are discussed with reference to previous results on sulfur-doped sodium halide crystals.
Measurements of Electrical Resistivity due to Phase Transformations in Indium-Rich Alloys
Authors: Fujita Yasuhiko , Nittono Osamu
Published: November 2005

This paper reports accurate measurements of the changes in electrical resistivity produced by the f.c.c. to f.c.t. (c/a>1) phase transformations in In-Cd, In-Pb and In-Tl alloys. It was found that, in the vicinity of the transformation temperature, In-Cd alloys show a step-like decrease in the electrical resistivity ρ(T); In-Pb alloys show a broad minimum ρ(T); and In-Tl alloys, show hardly any change in ρ(T) corresponding to the phase transformation. It was also found that, during the f.c.c.→f.c.t. transformation, the temperature coefficient α=(1/ρ)(d ρ/d
T) increases for In-Cd alloys but is constant for In-Tl alloys. The results on α are discussed using the resistivity formula including the electron-phonon spectral function αtr
2(ω)F(ω).
Coating Films of Titanium Nitride Prepared by Ion and Vapor Deposition Method
Authors: Satou Mamoru , Andoh Yasunori , Ogata Kiyoshi , Suzuki Yasuo , Matsuda Koji , Fujimoto Fuminori
Published: November 2005

Titanium nitride coating films were prepared on polished stainless steel and graphite plates by vacuum evaporation of titanium with simultaneous bombardment by nitrogen ions with an energy of 10 to 30 keV (IVD method). The compositional variations of each element with depth and the crystal structure were analysed by means of XPS, RBS and X-ray diffraction. It was confirmed that a significant intermixed layer exists at the interface. The thickness of this layer was about 440 Å for a film prepared on a stainless-steel plate at about 300°C by a 30 keV nitrogen ion beam, and decreased with decrease of the ion energy. Films were mainly composed of TiN crystallites with [100] axes preferentially oriented normal to the film surfaces. Some titanium was bound to oxygen and carbon atoms, but there were no metallic-state titanium atoms.
Measurement of Electron Mobility in p-Si by Time-of-Flight Technique
Authors: Morohashi Makoto , Sawaki Nobuhiko , Akasaki Isamu
Published: November 2005

The time-of-flight technique was studied as a method of measuring the the minority-carrier mobility in p-type Si. The ambipolar diffusion equations were solved numerically, and it was found that the transit time is given by the time from the initial rise to the shoulder at the fall of the induced current waveform rather than the half-height width, even if the ambipolar effects are strong. For example, the transit time defined by the former agreed with the true transit time within an error of 2%, while the latter gave an error of up to 10%. To demonstrate the usefulness of the method, the drift mobility of electrons in p-type silicon was studied and the results were compared with those for majority ones.
Pyroelectricity in Oriented Polytrifluoroethylene
Authors: Oka Yoshio , Koizumi Naokazu
Published: November 2005

Poling of oriented polytrifluoroethylene (PTrFE) was found to produce pyroelectricity which showed anomalous behavior and formation conditions identical to those in unoriented samples. The pyroelectric activity in oriented PTrFE was greatly enhanced when the poling temperature was low but was reduced as the poling temperature was raised, contrary to the behavior of ordinary thermoelectrets. The enhancement of the pyroelectricity is attributed to a greater increase of the new crystalline region and to the orientation effect, which aligned the dipoles along the electric field. The reduction of the pyroelectricity is attributed to an increase in the degree of chain orientation, which aligns the polar axis parallel to the film plane. This behavior depended strongly on the state of the amorphous region from which the new crystalline region carrying the spontaneous polarization grew.
A Study of Microstructures of Grain Boundaries in Sintered Fe77Nd15B8 Permanent Magnet by High-Resolution Electron Microscopy
Authors: Hiraga Kenji , Hirabayashi Makoto , Sagawa Masato , Matsuura Yutaka
Published: November 2005

The microstructures of the grain boundaries in an Fe77Nd15B8 permanent magnet have been examined by high-resolution electron microscopy, in samples quenched from the sintering temperature of 1350 K and in samples quenched and then annealed at 870 K. The coercivities of the quenched and the quenched-and-annealed samples were 500 and 1000 kA/m, respectively. Thin layers of a bcc phase were observed over the surfaces of most of the Fe14Nd2B grains in both samples. In the quenched sample, the interfaces between the bcc phase and the Fe14Nd2B grains were not so distinct, and many thin platelets of the bcc phase were found to extend from the interfaces to the inside of the Fe14Nd2B grains of which the surrounding lattice is compressed locally. In the annealed sample, the platelets disappear completely and the interfaces between the bcc phase and the Fe14Nd2B grains become very sharp and distinct. It is concluded that the morphology of the bcc phase, particularly the microstructure of its interface with Fe14Nd2B grains, controls the coercivity mechanism of Fe77Nd15B2.
Improved Counter-Electrode Used in Two-Dimensional Electrochromic Writing Board
Authors: Morita Hiroshi
Published: November 2005

In an attempt to eliminate coloring irregularity and variations in the response speed of ECDs utilizing tungsten oxide films, the electromotive force (EMF) originating in a cell was investigated as a possible cause of these undesirable characteristics. Sputtered metal-tungsten oxide cermit films were developed as an imporved method.
Furthermore, a prototype two-dimensional writing board was made using Ta-WO3 cermet film mounted on a counter electrode.
Photon Time-of-Flight Fluorescence Spectroscopy through an Optical Fiber
Authors: Watanabe Junji , Kinoshita Shuichi , Kushida Takashi
Published: November 2005

The feasibility of time-domain luminescence spectroscopy using an optical fiber as a dispersive element has been demonstrated for the fluorescence of hematoporphyrin in dioxane. A cw mode-locked Ar+ laser was used for the excitation, and a time-correlated single-photon counting technique for the detection. The effects of several time-broadening factors and possible applications of this spectroscopic method are discussed.
Sharp Spectra of Thermally-Stimulated Current in Tetracene Films
Authors: Sakurai Takao
Published: November 2005

Thermally-stimulated currents (TSC) with sharp spectra were observed in tetracene films deposited at room temperature and cooled rapidly after deposition. A TSC near 230 K was observed to depend on the film thickness, the existence of a bias voltage, the excitation wavelength, and the photocurrent, and appeared only in a vacuum. This TSC is thought to be due to an amorphous structure in the films. Its behavior shows that it is produced by charge-transfer excitons interacting with charge carriers.
As the amorphous structure disappeared, polycrystallization occurred in the films.
Annealing Effect on Hydrogenated Amorphous Silicon Films Prepared at High Deposition-Rate by Substrate Impedance Tuning Technique
Authors: Ueda Masato , Chayahara Akiyoshi , Nakashita Toshio , Imura Takeshi , Osaka Yukio
Published: November 2005

The annealing-induced changes in the infrared absorption, optical absorption, electron spin resonance and photoluminescence of hydrogenated amorphous silicon deposited at a high deposition-rate of ∼4.5 nm/s were investigated. The photoluminescence intensity increased, while the band-tail absorption decreased greatly when the sample was annealed up to 400°C. The silicon-hydrogen bonding configuration varied with annealing in a completely different manner from that of low-rate (∼0.1 nm/s) films. The mode of atomic stacking in high-rate as-deposited films appears to deviate appreciably from that in low-rate ones.
Synthesis and Characterization of Si3N4 Powder Produced by Laser-Induced Chemical Reaction
Authors: Kizaki Yoshimi , Kandori Toshio , Fujitani Yoshiyasu
Published: November 2005

In an attempt to prepare very fine, high-purity Si3N4 powder from an NH3/SiH4 system by CO2 laser induced reaction, the reaction parameters relating to the laser operation and the reaction conditions were examined systematically. Both pulsed and continuous high-power CO2 lasers were used, the Si3N4 powders obtained exhibited various colors from brown to white. Their particle size was 10∼15 nm, and their nitrogen content was 37 wt%. The powders were composed of amorphous and partially-crystallized particles. The α-transformation in the heat treatment of two typical samples up to 1600°C was investigated by X-ray diffraction, and the surface area reduction produced by the heat treatment was also measured. The factors affecting the synthesis of the Si3N4 powder were found to be the NH3/SiH4 ratio, the reaction pressure, and the laser power density.
A Study on LPE Growth of In1-xGaxP1-yAsy(y ≃0) on (100) GaAs Substrate
Authors: Kondo Masahiko , Shirakata Sho , Tsushi Akihito , Nishino Taneo , Hamakawa Yoshihiro
Published: November 2005

The growth conditions have been studied in detail for InGaPAs LPE layers grown on (100) GaAs substrates using the two-phase melt technique. The accurate liquidus isotherms and iso-concentration curves have been obtained experimentally and are compared with the calculated ones. It has been found that the area of the successful growth of InGaPAs on GaAs shifts according to the degree of supercooling. The influences of variations of the As atomic fraction in the liquid, X
As
l, on the liquidus and solidus compositions have also been investigated in detail. The diffusion coefficients of P and Ga in an In-rich melt at 800°C have been determined as 1.9×10-4 and 1.8×10-4 cm2/s, respectively. The influence of the degree of supercooling on crystal growth is discussed using a mass transport analysis in both liquid and solid phases, together with the equilibrium phase diagram.
Warpage of Czochralski-Grown Silicon Wafers as Affected by Oxygen Precipitation
Authors: Shimizu Hirofumi , Watanabe Tetsuo , Kakui Yoshiharu
Published: November 2005

The warpage of Czochralski-grown silicon wafers was investigated in relation to oxygen precipitation caused by simulated heat-treatments at 1000°C and LSI processing, using specimens cut from measured positions along the crystal length. The warpage of the wafers due to simulated thermal stresses increases with the concentration of precipitated oxygen atoms associated with the formation of SiO2 precipitates observed in infrared spectra at around 1224 cm-1, reaching a maximum in the seed-end and a minimum in the tail-end wafers. LSI processing experiments showed that the microdefect density resulting from the nuclei in as-grown ingots must be equal to or lower than 5×109 cm-3 to reduce the warpage and improve the chip yield of devices, even if the microdefect density in the bulk is increased to aim at the intrinsic gettering effect.
Barrier Effects of Tungsten Infer-Layer for Aluminum Diffusion in Aluminum/Silicon Ohmic-Contact System
Authors: Hara Tohru , Enomoto Shuichi , Ohtsuka Noboru , Shima Shohei
Published: November 2005

The barrier effects of tungsten inter-layers for aluminum diffusion have been studied in an aluminum/silicon ohmic-contact system, where the tungsten layers were deposited by chemical vapor deposition (CVD) and sputtering. Sintering was carried out at temperatures ranging from 450°C to 550°C and the interfacial reaction was then studied by 1.5 MeV He+ Rutherford backscattering spectroscopy. In the CVD tungsten infer-layer, no discernible reaction took place at each interface up to 500°C. However, reaction occurred at the aluminum-silicon interface in sputtered tungsten even at 450°C, and a WA112 compound was formed, indicating the achievement of a sufficient barrier effect in the CVD layer at 500°C. Tungsten diffused to the aluminum and/or the silicon at 550°C in both samples, and tungsten silicide layers were formed at the tungsten-silicon interface.
Effect of Carrier Gas on Structure of Plasma Polymerized Tetrafluoroethylene Films
Authors: Nakano Toshiki , Kasama Yasuhiro , Ohki Yoshimichi , Yahagi Kichinosuke
Published: November 2005

Thin films were polymerized by introducing tetrafluoroethylene gas into the “tail-flame” of a glow discharge of hydrogen or argon used as a carrier gas. Compared with argon, hydrogen gives a higher deposition rate at low discharge power and a lower rate at high discharge power. ESR, ESCA and IR measurements showed that films polymerized using hydrogen as a carrier gas are crosslinked to a higher degree and have more radicals than those polymerized using argon. The former films have higher tan
δ values than the latter films. These results arise from the competing processes of polymerization and ablation in the glow-discharge plasma.
A High-Capacitance Trench Structure (Hi-CAT) for Megabit LSI Memories
Authors: Satoh Shin-ichi , Yoneda Masahiro , Fujishima Kazuyasu , Yamazaki Teruhiko
Published: November 2005

A new memory capacitor named “Hi-CAT” has been developed and used in fabricating a 256 kbit dRAM. The Hi-CAT structure was produced by forming a trench on a P-/P+ substrate using reactive ion etching (RIE). The new structure gives a storage capacitance (C
s) 1.56 times greater and a soft error rate 800 times less than those given by three other types of structure (conventional (a), epi-sub (b) and trench (c)). The additional junction capacitance and collection efficiency of the new structure are discussed, and the pause-refresh characteristics of the 256 kbit dRAM made with the structure show the feasibility of the new structure for use in future megabit LSI memories.
Experimental Studies on the Hot Electron Rings in NBT-1M
Authors: Tsuchidate Hiroyuki , Hosokawa Minoru , Fujiwara Masami , Ikegami Hideo
Published: November 2005

The scaling characteristics of the high-beta hot-electron rings in NBT-1M were studied experimentally. The hot electron temperature T
h and the density n
h were measured by the hard X-ray detection system, and were found to have typical values of 220 keV and 3×1010 cm-3, respectively. The stored energy of the hot electron ring, W
⊥, scales empirically with the applied microwave power P
µ and the ambient gas pressure P
H2
as W
⊥ ∝P
µ
P
H2

-1 in the quiescent T-mode. The dependence of the energy stored in the ring on the gas pressure in the T-mode can be explained by the simple energy balance equation. In T-mode operation, the temperature is independent of the applied microwave power, but the density increases with the power and decreases with the gas pressure.
Analysis of Optimal Feedback Control of Vertical Plasma Position in a Tokamak System
Authors: Moriyama Shin-ichi , Nakamura Kazuo , Nakamura Yukio , Itoh Satoshi
Published: November 2005

An optimal control method was used to control the vertical position of a non-circular plasma with negative n-indices in a tokamak system. Taking the time delays in the control devices into consideration was found to improve the optimal feedback control law. Transient-response analysis of the control system in the TRIAM-1M tokamak showed that the optimal control technique can be used to control the plasma position in the stable region and that the ultimate lower limit of the n-index for the stabilization can be close to the limit n
c for the fast-growing mode of positional instability.
In addition, a pulsewidth-modulated inverter power supply with gate turn-off thyristors is proposed as a feedback power supply. This power supply has enabled the optimal position control of highly-elongated plasmas to be carried out an actual tokamak system.
Physical Properties of Laser-Produced Dense Plasma in High-Pressure Argon Gases
Authors: Yamada Jun , Tamano Takamichi , Okuda Takayoshi
Published: November 2005

High-pressure gaseous argon at pressures up to 200 atm was irradiated by a ruby laser to study the physical properties of the laser-produced plasma. High-density plasmas with an electron density of the order of 1020∼1021 cm-3 were obtained. At low pressure, a nearly complete ionized state was achieved, and as the gas pressure increased, the degree of ionization decreased. The electron temperature was of the order of 105 K and increased slightly with increasing pressure. The hot plasma was conical with its apex at the focal point, and the radius of the plasma depended only on the axial position. As the pressure increased, the plasma extended axially in front of and behind the focal spot. This phenomenon is interpreted as the result of a change in the refractive properties of the high-pressure gas.
Effects of Anisotropic Excitation in Laser-Induced Fluoresceruce Spectroscopy (LIFS)
Authors: Fujimoto Takashi , Goto Chiaki , Uetani Yasunori , Fukuda Kuniya
Published: November 2005

Various features of the effect of alignment in the upper-level population on the observed emission-line intensity, i.e., the spatially-anisotropic intensity distribution and polarization, are demonstrated using laser-induced fluorescence spectroscopy on the neon 2p
53s-2p
53p transitions in a plasma. Disalignment by atomic collision is observed on the 2p
2 level, and its rate coefficient is determined as (1.70 ±0.03) ×10-10 cm3s-1. The case of hyperfine-structure lines is discussed. Polarization is observed in the hydrogen Balmer α line fluorescence following the laser excitation of the same transition. Conditions are given under which the alignment effect is eliminated or can be neglected. Cases of unpolarized-light excitation and high-intensity excitation are discussed.
9 ps Gate Delay Josephson OR Gate with Modified Variable Threshold Logic
Authors: Fujimaki Norio , Kotani Seigo , Hasuo Shinya , Yamaoka Toyoshi
Published: November 2005

A Josephson logic OR gate suitable for high speed logic circuits is proposed and tested. This gate has a structure modified from Variable Threshold Logic (VTL) to obtain large operating margin and small occupation area. The operating margin is calculated as ±19% for fan-out of 2, even with the critical current variation of ±20%. The circuit area is 40×60 µm2. A chain of 5-stage OR gates was fabricated. The gates had Josephson junctions of 4 µm and 7 µm diameter made with Pb-alloy technology. The minimum gate delay of 9 ps was measured using a Josephson sampler.
Comparison between GaAs and AlxGa1-xAs Quantum Wells in the Light Emission Limit
Authors: Iwamura Hidetoshi , Saku Tadashi , Hirayama Yoshiro , Okamoto Hiroshi
Published: November 2005

Photoluminescence properties were compared between two types of multi-quantum-well (MQW) structures. One of them had a potential well layer composed of binary GaAs, and the other was composed of ternary Al
x
Ga1-x
As. It is shown that the ternary well MQW structure is more favorable with respect both to higher emission energy and to photoluminescence linewidth than the binary well MQW structure.
New Photoresist for High Resolution Two-Layer Resist Systems
Authors: Tanaka Akinobu , Morita Masao , Onose Katsuhide
Published: November 2005

We propose a new photoresist MSNR (Methacrylated Silicone-based Negative Resist) for high resolution two-layer resist systems. This photoresist shows high sensitivity to near-UV light (350–450 nm), D
0.5=40 mJ/cm2, and excellent resistance to reactive ion etching under oxygen gas. A submicron (0.7 µm) patterns with a high aspect ratio can be easily fabricated with MSNR/AZ two-layer resist systems using near-UV lithography.
Molecular Beam Epitaxy of InP Using Low Energy P+ Ion Beam
Authors: Shimizu Saburo , Tsukakoshi Osamu , Komiya Souji , Makita Yonosuke
Published: November 2005

A new film growth technique of III-V compound semiconductors is developed where the sticking coefficient of the group V element can be increased by implanting mass separated, high purity group V ion at low energy. Using this growth technique, the epitaxial growth of InP on (100)InP substrate is studied.
Single crystal films are grown between 210°C and 420°C at the P+ ion energy of 200 eV and with the flux intensities of In molecular beam and P+ ion beam of 1.5×1013 cm-2·s-1 and 3.0×1013 cm-2·s-1, respectively. The films grown between 300°C and 420°C show sharp 2×4 structure in the RHEED pattern as in the case of MBE, and also show well defined features due to bound excitons and donor-acceptor pairs in the photoluminescence spectra at 4.2 K.
Observation and Analysis of Visible Overtone Band Transitions of NH3
Authors: Kuga Takahiro , Shimizu Tadao , Ueda Yoshifumi
Published: November 2005

A sensitive spectrometer with a ring dye laser is constructed to observe very weak visible transitions of molecules. The sensitivity is estimated to be 3×10-9/cm in the absorption coefficient.
About 1000 high overtone and combination band lines with Δ
v=5 of NH3 are observed in the frequency range 15260–15590 cm1. Among them, 193 lines are assigned and the rotational constants in the highly excited vibrational states are determined.
Maskless Ion Beam Assisted Etching of Si Using Chlorine Gas
Authors: Ochiai Yukinori , Shihoyama Kazuhiko , Masuyama Akio , Gamo Kenji , Shiokawa Takao , Toyoda Koichi , Namba Susumu
Published: November 2005

Characteristics of maskless ion beam assisted etching of Si have been investigated as a function of chlorine gas pressure. Focused Ga ion beam was irradiated on a Si substrate in chlorine gas atmosphere at a pressure ranging from 0 to 24 mTorr. The etching rate exhibited a maximum at a pressure of 8 mTorr, the value of which was about 5 times larger than the physical sputter etching rate, and decreased at higher chlorine gas pressure. At a pressure of 8 mTorr, the chlorine atom arrival rate was about 4 times larger than the Si removal rate. This ratio suggests that Si is mainly removed by forming volatile SiCl4.
Pressure Effect on Ferroelectric Phase Transition of Vinylidene Fluoride-Trifluoroethylene Copolymer (54/46 mol%)
Authors: Matsushige Kazumi , Horiuchi Toshihisa , Taki Seiji , Takemura Tetuo
Published: November 2005

Pressure effects on the ferroelectric phase transition of a vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymer with 54 mol% VDF content have been investigated by means of DTA and X-ray diffraction methods up to 400 MPa. At high pressures above 200 MPa this copolymer exhibited multiple DTA peaks upon a ferro-to-paraelectric phase transition and a temperature hysteresis in the transition points. Correspondingly, the results of high pressure X-ray diffraction measurements showed the singular temperature variation of (200, 110) reflections, suggesting the pressure-induced structural transformation.
Far Infrared Spectroscopy by the Fabry-Perot Interferometer IV
Authors: Yoshihara Kunio , Zhao Bao-Chang , Kitade Atsuo
Published: November 2005

Using the method of solution of Hilbert and Schmidt, the spectrum of radiation is recovered from an integral equation expressing the relation between the spectrum and its multiple-beam interferogram. The instrumental function does not show the noticeable side lobes which appear in Fourier spectroscopy, and, in addition, the resolution is greatly improved.
The Effects of Carrier Concentration Dependent Diffusion Coefficient on the Lateral Profile of Injected Carriers in Stripe Geometry Lasers
Authors: Tanguy Ch.
Published: November 2005

For the first time, a model is presented that takes the effects of concentration-dependent coefficient diffusion into account to determine the lateral distribution of injected carriers in an active layer of gain-guided stripe-geometry lasers. In high carrier concentration cases, computed examples demonstrate the lack of accuracy of the other classical models.
Polytypes and Intergrowth of the Intermetallic Compounds Sm2Ni7
Authors: Horikoshi Hideharu , Takeda Seiji , Komura Yukitomo
Published: November 2005

Intermetallic compounds in the Sm-Ni system whose compositions are near Sm2Ni7 have been studied by high-resolution electron microscopy. Four new polytypes of 4H, 5T, 9R and 12R, the intergrowth of Sm5Ni19 in between the matrix of Sm2Ni7, stacking faults and several defect structures are found in the specimens, and their structures are analysed by high-resolution lattice imaging method combined with electron diffraction.
Gas Source MBE Growth of High-Quality InP Using Triethylindium and Phosphine
Authors: Kawaguchi Yoshihiro , Asahi Hajime , Nagai Haruo
Published: November 2005

High-quality InP layers have been grown on (100) InP substrates by gas source molecular beam epitaxy using triethyl-indium and phosphine as III and V group sources. The electrical and optical properties of grown InP films are evaluated and compared with those of films grown using red phosphorus as a P source. Epitaxial layers are n-type and the highest achieved 77 K mobility is 24000 cm2/Vs with a carrier concentration of 4.1×1015 cm-3. When phosphine is used instead of red phosphorus as a P source, the compensation ratio (NA/ND) decreases from 0.60–0.98 to 0.29–0.31.
Optical Microscope Observation of Hexagonal Ordering in Surface Stabilized Ferroelectric Liquid Crystal Cells
Authors: Uemura Tsuyoshi , Ouchi Yukio , Ishikawa Ken , Takezoe Hideo , Fukuda Atsuo
Published: November 2005

The molecular alignment in smectic phases with hexagonal ordering has been studied by observing surface stabilized ferroelectric liquid crystal cells of 8SI* and HxOBAMBC under an optical polarizing microscope. There findings are: (1) Continuous degeneracy in tilt direction is lifted and is replaced by the discrete one specified by azimuthal angles φ=0, ±π/3, ±2 π/3 and π. (2) One of the sides of hexagon is parallel (SJ
*) or perpendicular (SG
*) to the bounding surfaces, so that the most stable molecular orientation is parallel to the cell surface in every phase. (3) The more the hexagonal ordering develops, the less stable the twisted states become.
Visible InGaP/GaAsP Dual Wavelength Light Emitting Diodes
Authors: Shima Akihiro , Fujii Sadao , Sakai Shiro , Umeno Masayoshi
Published: November 2005

Visible dual wavelength light emitting diodes (LED's) have been successfully fabricated growing lattice matched In0.3Ga0.7P on GaAs0.6P0.4 commercial epitaxial substrate on GaAs. InGaP and GaAsP homojunction LED's have respective emission wavelength of 583 nm and 652 nm and cutoff frequencies of 8 MHz and 12 MHz.
Photoconductive Amorphous Silicon-Carbide Produced by Intermediate Species SiF2 and CF4 Mixture
Authors: Matsumura Hideki , Uesugi Takashi , Ihara Hisanori
Published: November 2005

A new type of amorphous silicon-carbide film is produced by the glow discharge decomposition of an intermediate species SiF2, CF4 and H2 gas mixture. Optical band gap and photoconductive properties of this film are measured as a function of carbon content. It is found that the optical band gap can be increased up to 2.2 eV by increasing carbon content without apparent degradation of film properties such as photoconductivity and photosensitivity.
Theorem on the Expected Number of Zeros of a Sine Wave Plus Random Noise
Authors: Sato Hiroshi , Tanabe Masami
Published: November 2005

It is proved that the expected number of zeros of a periodic wave plus random noise is independent of the amplitude of the periodic wave if and only if the periodic wave is a sinusoidal wave with frequency equal to half the expected number of all zeros of the random noise only. The relation of this result to the “periodic wave process” plus random noise is discussed.
Photoelectrochemical Cell Using Polythiophene Film
Authors: Kaneto Keiichi , Ishii Gaku , Yoshino Katsumi
Published: November 2005

A photoelectrochemical solar cell is fabricated using polythiophene film as an active photoelectrode and a lead plate as a counter electrode in Pb(ClO4)2/acetonitrile electrolyte. Open circuit voltage of ca. 0.8 V and short circuit current of ∼0.2 mA/cm2 with a conversion efficiency of greater than 0.03% are obtained under illumination of approximately 1 sun. Photoinduced charging of the cell is also demonstrated for a long period of illumination, indicating possible application as a cell with photovoltaic element and rechargeable battery functions.
Structural Change in Cr Microneedles Induced by Magnetic Field
Authors: Okuyama Fumio , Fujimoto Yasutaka
Published: November 2005

It is shown that the crystal structure of Cr microneedles growing in a strong electrostatic field is affected by an external magnetic field. The needles grown below 1000 G are fcc with lattice constant 4.10–4.12 Å, as determined by electron diffraction. The structure above 1000 G is the normal bcc structure with lattice constant 2.87–2.89 Å. Presumably, a high magnetic field modifies the distribution of electrostatic charges in the growing needles, thereby causing the structural change.
Electronic Conduction in Mg Doped In2O3 Single Crystals
Authors: Kanai Yasuo
Published: November 2005

Mg doped In2O3 single crystals are prepared by flux method and their electronic conduction is investigated. Since Mg acts as an acceptor impurity, electrical resistivity of the In2O3 crystal increases and electron concentration decreases by doping with Mg. The crystals are n-type and the lowest value of electron concentration is about 2×1016/cm3. The electron concentration and electron mobility of the crystals are found to be almost independent of the temperature. The experimental results are explained by assuming that the acceptors, Mg ions which replace In ions, are almost completely compensated by the native donors, the oxygen vacancies, in In2O3 crystals.
Chemical Analysis of Surfaces by Total-Reflection-Angle X-Ray Spectroscopy in RHEED Experiments (RHEED-TRAXS)
Authors: Hasegawa Shuji , Ino Shozo , Yamamoto Youiti , Daimon Hiroshi
Published: November 2005

A new method for chemical analysis of surfaces by total-reflection-angle X-ray spectroscopy in RHEED experiments (RHEED-TRAXS) has been developed. When the X-ray take-off angle is set to be the critical angle for total reflection of the characteristic X-ray emitted from the deposited atoms on surfaces, the detection efficiency for the deposit becomes drastically higher owing to the refraction effect of the X-ray. This enhancement of surface sensitivity is demonstrated with Ag on Si(111). The smallest detectable amount of Ag is about 0.01 monolayer or less. This sensitivity is comparable to or higher than that of AES.
Experimental and Theoretical Two-Dimensional X-Ray Photoelectron Diffraction Patterns from GaAs(001) Surface
Authors: Owari Masanori , Kudo Masahiro , Nihei Yoshimasa , Kamada Hitoshi
Published: November 2005

Two-dimensional X-ray photoelectron diffraction (XPED) patterns were obtained from a GaAs(001) sample as functions of both polar and azimuthal angles. Corresponding theoretical calculations based on the single scattering model were also made. Theoretical results agreed very well with experiments both for Ga3d and As3d photoelectrons. Ga3d and As3d photoelectrons showed different XPED patterns which reflect the difference of the atomic sites in the crystal, although their symmetric property was the same as that of the crystal.
Influence of MBE Growth Conditions on Persistent Photoconductivily Effects in N-AlGaAs and Selectively Doped GaAs/AlGaAs Heterostructures
Authors: Ishikawa Tomonori , Kondo Kazuo , Hiyamizu Satoshi , Shibatomi Akihiro
Published: November 2005

The influence of MBE growth conditions on persistent photoconductivity effects has been investigated both for N-Al0.3Ga0.7As layers and for selectively doped GaAs/N-Al0.3Ga0.7As heterostructures. The concentration of DX centers in the N-AlGaAs layer was proved to be independent of growth conditions, suggesting no relation to any native defect. For the selectively doped GaAs/N-AlGaAs heterostructure, in addition, persistent increase in 2DEG concentration after light exposure at 77 K was also proved to be independent of growth conditions.
Atomic Structure Images Formed by Plasma-Loss Electrons
Authors: Ajika Natsuo , Hashimoto Hatsujiro , Yamaguchi Koji , Endoh Hisamitsu
Published: November 2005

Two kinds of energy filtered atomic structure images of Si crystal in (011) orientation formed by no-loss and plasma-loss electrons were photographed using the energy analyzer of a sector type magnet which was attached to the bottom of a high resolution electron microscope.
The behavior of plasma-loss electrons in the crystal was discussed on the basis of the dynamical theory of electron diffraction. The contrast of the crystal lattice image formed by the plasma-loss electrons was calculated and compared with the observed image.
Ta-O (Ta-oxide) and Nb-O (Nb-oxide) Film Deposition Using an Electron Cyclotron Resonance Plasma
Authors: Watanabe Iwao , Yoshihara Hideo
Published: November 2005

The low temperature depositions (under 200°C) of Ta-O and Nb-O films are investigated using microwave ECR (electron cyclotron resonance) plasma deposition with Ta-halide or Nb-halide and O2 as raw material gases. High deposition rate (400 Å/min) is easily obtained with Ta-chloride and Nb-chloride, however, with Ta-fluoride and Nb-fluoride the deposited films at 200 Å/min have low resistance against humidity due to their fluoride content. The refractive indices of the Ta-O and Nb-O are 2.15 and 2.2 at 6328 Å. The structures of both films are amorphous. They are stable up to 400°C.
Growth-Interrupted Interfaces in Multilayer MBE Growth of Gallium Arsenide
Authors: Takamori Akira , Miyauchi Eizo , Arimoto Hiroshi , Bamba Yasuo , Morita Tetsuo , Hashimoto Hisao
Published: November 2005

Growth-interrupted interfaces in Molecular Beam Epitaxy (MBE) have been characterized by C-V measurements and secondary ion mass spectroscopy. Carriers were depleted around the interfaces depending on interruption conditions such as the background vacuum and the interrupted period. For the depleted samples, carbon was detected at the interfaces. This carbon contaminant deteriorated crystal quality at the interface and caused carrier depletion. Using the MBE system combined with a maskless ion implanter in ultrahigh vacuum (UHV), a selectively Si-implanted GaAs multilayer structure was grown without interface degradation.
Grain Growth and Conductive Characteristics of Super Thin Polysilicon Films by Oxidation
Authors: Noguchi Takashi , Hayashi Hisao , Ohshima Takefumi
Published: November 2005

Improved characteristics of electronic conduction and grain growth effect of super thin CVD polysilicon films after thermal oxidation (less than 1000 Å thick) were investigated. After oxidation of CVD silicon, grain size grew two-dimensionally to as large as 1500 Å in diameter with a thickness of 300 Å. In contrast, temperature dependence of conductivity changed from T
-(1/4) rule to T
-1 rule after oxidation. The grain growth effect after oxidation to super thin films (200–300 Å thick) was found to affect the decrease in grain boundary barrier height, which resulted in the increase of carrier mobility.
Acoustic Radiation Induced by Intensity Modulated Ion Beam
Authors: Kimura Kenji , Nakanishi Kenji , Nishimura Akira , Mannami Michi-hiko
Published: November 2005

The acoustic radiation induced by an intensity modulated beam of H+ ions whose energies lie in the range 15–30 keV in solids was observed. The acoustic signal is proportional to the incident power of the ion beam and to the inverse of the frequency of the modulation. This result is explained by the theory of Jackson and Amer which describes the photoacoustic radiation. A change in the acoustic signal by the deposition of gold layer on the silicon target was observed. This suggests the applicability of this ion induced acoustic radiation to investigation of the solid surface layer.
Optical Waveguide Dispersion in Quantum Well Structures
Authors: Walpita L. M.
Published: November 2005

Optical waveguide dispersion in multi-quantum well structures is determined. A multi-quantum well structure can be described by an equivalent step index waveguide having the same dispersion characteristics. Limitations of this assumption are discussed for the GaAs/GaAsAs structure.
Effect of the Soft X-Ray Standing Wave Fields on the Total Electron Yield Spectra from an InP Crystal
Authors: Ohta Toshiaki , Sekiyama Hideo , Kitajima Yoshinori , Kuroda Haruo , Takahashi Toshio , Kikuta Seishi
Published: November 2005

We observed the electron emission modulated by a standing wave field from an InP (100) single crystal in the soft X-ray region. Incident photon energy was scanned with a total electron detector, instead of scanning the incident angle to the sample. A remarkable difference of electron yield profiles was observed between below and above the P K edge. This difference can be understood by considering the drastic change of the P K absorption coefficient. It is also suggested that the soft X-ray standing wave method is a promising technique for the structure analysis of semiconductor surfaces.
Simple Method for Measuring the Sound Velocity of a High Absorption Liquid
Authors: Matsuzawa Kiichiro , Inoue Naoki , Hasegawa Takahi
Published: November 2005

A new method for measuring the phase velocity at MHz frequencies is presented. Two quartz transducers are separately placed; the time difference between the ac-voltage pulse (tone burst) applied to the transmitting transducer and the out-put-voltage pulse of the receiving transducer is measured with an accuracy of several percent of the period of resonant vibration of the transducers. A special technique is used in order to find the cycle-for-cycle matching between the two pulses. The measurement is easily performed even with a liquid of 40 dB absorption between the two transducers.
Polycrystalline Thin-Film TiO2/Se Solar Cells
Authors: Nakada Tokio , Kunioka Akio
Published: November 2005

A new type of selenium solar cell with a titanium dioxide (TiO2)/Se heterojunction has been fabricated by low-cost process. An efficiency of 5.01% under AM 1.5 illumination (100 mW/cm2) has been achieved without antireflection coatings. The corresponding short-circuit current density, open-circuit voltage, and fill factor are 10.8 mA/cm2, 0.884 V, and 0.525, respectively. The efficiency is the highest among Se-based solar cells reported to date. These cells also have extremely high spectral response at short wavelengths, resulting in efficiencies of 11–13% under fluorescent light (500 lux).
ESR Studies on the Light-Induced Effect in Si-Based Amorphous Semiconductors
Authors: Yokomichi Haruo , Kumeda Minoru , Morimoto Akiharu , Shimizu Tatsuo
Published: November 2005

Light-induced creation of defects and their decay by annealing are investigated by means of ESR in a-Si:H, a-Si1-x
N
x
:H and a-Si1-x
C
x
:H. The amount of increase in the ESR spin density by prolonged strong illumination is found to increase with an increase in the structural flexibility factor defined by the inverse of the average coordination number, regarding an H atom bonded to Si, C or N as an entity reducing the coordination number by one.
Coherent Growth of ZnSe on GaAs by MOCVD
Authors: Mitsuhashi Hiroshi , Mitsuishi Iwao , Mizuta Masashi , Kukimoto Hiroshi
Published: November 2005

The lattice parameters of ZnSe have been studied for epitaxial layers of different thicknesses grown on GaAs (100) substrates by metalorganic chemical vapor deposition (MOCVD) using dimethylzinc and diethylselenide as source materials. The results indicate that layers thinner than 0.15 µm can grow coherently on GaAs involving strains due to the lattice mismatch between ZnSe and GaAs, while thicker layers contain misfit dislocations introduced by the relaxation of strain.
Application of a Schottky Barrier Diode Mixer to a 118.8 µm Laser Interferometer
Authors: Tetsuka Tsutomu , Okajima Shigeki , Kawahata Kazuo , Fujita Junji
Published: November 2005

Fundamental characteristics of a GaAs Schottky barrier diode mixer have been measured for the purpose of using it as the detector of a twin 118.8 µm CH3OH laser interferometer. The mixer sensitivity for beat oscillations of the twin lasers was measured in a frequency region from 1 MHz to 7 MHz. A signal to noise ratio of I.F. signal over 45 dB is obtained for the frequency up to 6 MHz. The dependence of the mixer sensitivity on local beam power was also measured. The I.F. signal level is approximately proportional to the local beam power in power level from 0.1 mW to 1.2 mW.
Si Depth Profiles in Focused-Ion-Beam-Implanted GaAs
Authors: Bamba Yasuo , Miyauchi Eizo , Nakajima Masato , Arimoto Hiroshi , Takamori Akira , Hashimoto Hisao
Published: November 2005

Depth distribution of implanted Si into GaAs using a focused-ion-beam (0.2 µm diameter, 160 keV) was profiled by means of differential Hall effect measurement and secondary ion mass spectroscopy. As compared to conventional unfocused-ion-beam implantation, implantation with a focused ion beam of high current density at high doses results in broadened profiles of the implanted Si at greater depths. This is probably caused by radiation-enhanced migration of the implanted Si during implantation.
Optical Properties of Aluminum Doped Zinc Oxide Thin Films Prepared by RF Magnetron Sputtering
Authors: Minami Tadatsugu , Nanto Hidehito , Takata Shinzo
Published: November 2005

The detailed study of optical transmittance and reflectance in Al-doped ZnO thin films prepared by rf magnetron sputtering is described. Films obtained with Al2O3 content up to 10 wt% showed an average transmittance above 85% in the visible range. The absorption edge was blue-shifted with increasing carrier concentration. The shift was interpreted to be a result of competition between many body effects and the Burstein-Moss effect. It is shown that films obtained with an Al2O3 content of 1–2 wt% can achieve an excellent IR shielding.
The δ-Doped Field-Effect Transistor
Authors: Schubert E. F. , Ploog K.
Published: November 2005

A new Schottky-gate FET grown by molecular-beam epitaxy is presented. A V-shaped potential well with a 2D electron-gas is generated in the epi-layer by implementation of a δ-function like doping profile. The δ-doped FET is scaled down to its ultimate physical limit normal to the crystal surface. The advantages of the new device are high gate-breakdown voltage, high transconductance due to the proximity of the electron channel to the crystal surface, and high electron concentration in the channel. Current-voltage and capacitance-voltage measurements reveal a large breakdown voltage and a narrow impurity and carrier distribution.