bluuebunny/crossref_metadata_2025 huggingface dataset:
Antiferroelectric Chiral Smectic Phases Responsible for the Trislable Switching in MHPOBC
Authors: Chandani A. D. L. , Gorecka Ewa , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

At least two antiferroelectric liquid crystalline phases were discovered in MHPOBC. These phases appear below the usual ferroelectric Sm C* phase. Because of the alternation of the molecular tilt directions as well as the dipole orientations in successive layers, the optic axis is along the layer normal. This strong stabilization along the layer normal brings about the so-called third stable state responsible for the tristable switching. The antiferroelectric structure was strongly supported by selective reflections in oblique incidence; a full-pitch band does not appear in the antiferroelectric phases, while it does appear in the ferroelectric phase.
Reinvestigation of the Structure of Si(111) √3 × √3-Ag Surface
Authors: Kono Shozo , Abukawa Tadashi , Nakamura Natsuo , Anno Koh-ichi
Published: February 2005

Critical Ag coverage of the Si(111) √3 × √3-Ag surface has been examined by µ-probe Auger electron spectroscopy and found to be one monolayer, consistent with results of other conventional surface spectroscopies. Analyses of previously reported X-ray photoelectron diffraction patterns have indicated that symmetric 1-monolayer models, including a recent honeycomb chained triangle model (Jpn. J. Appl. Phys. 27 (1988) L753) and its derivatives, are unlikely. An asymmetric 1-monolayer model is presented from the analysis of X-ray photoelectron diffraction and is to be tested by other methods.
Substitution Effects of Pb for Bi on the Formation of High-Tc Superconducting Thick Films in the Bi-Pb-Ca-Sr-Cu-O System by the Melt-Solidification Method
Authors: Tohge Noboru , Akamatsu Yoshinori , Tsuboi Shinzo , Tatsumisago Masahiro , Minami Tsutomu
Published: February 2005

Superconducting thick films of Bi1.8Pb0.2Ca2Sr2Cu3O
x
have been prepared by the melt-solidification process. The mixtures of oxides or carbonates of each metal were melted on MgO single-crystal substrates at 1000°C for 5 min and then held for crystallization at various temperatures and for various periods. The holding at 850°C for 15 h produced thick films with T
c(zero) at 102 K owing to the deposition of the 110 K phase along with the 80 K phase, both phases being highly c-axis orientated. This is indicative of the effectiveness of the substitution of Pb for a part of Bi for the deposition of the 110 K phase in the melt-solidification process.
Control of Oxygen Deficiency in Superconducting Y1Ba2Cu3O7-y Films Using a Solid-State Electrolyte
Authors: Yugami Hiroo , Watanabe Tsuyoshi , Suemoto Tohru , Shin Shik , Sobajima Shigenobu , Ishigame Mareo
Published: February 2005

Y1Ba2Cu3O7-y
(YBCO) films deposited on YSZ are coated with MgO films in order to isolate the YBCO film from the atmosphere. An electrochemical technique using a solid-state electrolyte is applied to this airtight structure to control the density of the oxygen deficiency y in the YBCO film. The resistivity of the YBCO film at 500°C is found to be reversibly changed by the applied current. The change of y by the applied current is confirmed by the change of the lattice parameter c. From the temperature dependence of the resistivity of the film, it is shown that T
c could be controlled and fixed by using this technique.
Damage Caused by RF Oxygen Plasma Asher
Authors: Samukawa Seiji
Published: February 2005

A new method for investigating the influence of stored charge and mobile ion contamination during photoresist ashing is proposed and is discussed with respect to the effect of the downstream on the photoresist ashing process.
The results of leakage current of CMOS inverter circuits and the threshold voltage shifts of field MOS transistors with aluminum gates indicate that RF oxygen downstream with baffle is very effective in preventing the influence of stored charge and mobile ion contamination.
Third-Harmonic Susceptibility in Single-Crystal YBa2Cu3O7-x Thin Films
Authors: Yamamoto Kazunuki , Mazaki Hiromasa , Yasuoka Hiroshi , Hirata Kazuto , Terashima Takahito , Iijima Kenji , Bando Yoshichika
Published: February 2005

Higher-harmonic susceptibility was investigated for single-crystal YBa2Cu3O7-x
thin films located in the ac magnetic field perpendicular to the film plane. We found for the first time that the third-harmonic term of the thin films has nonzero values in the region of ac-susceptibility transition. The nonlinear response against ac magnetic field indicates that the Maxwell-Strongin model is not applicable and there must be some mechanism obstructing the vortex motion in the films.
Superlattice Structure of Bi2Sr2GdCu2O8+y
Authors: Sato Shoichi , Tamegai Tsuyoshi
Published: February 2005

An approximate superstructure of Bi2Sr2GdCu2O8+y
was determined by single-crystal X-ray diffraction. The crystal is isomorphic with those of both Bi2Sr2YCu2O8+y
and superconducting Bi2Sr2CaCu2O8+y
; the structure is modulated along the fundamental b
0 axis. The true modulation period is 8b
0, but can be regarded as 4b
0 for a good approximation. The approximate structure is orthorhombic, space group I
m
c
b; a=5.4514(9), b=4b
0=21.948(3) and c=30.221(4) Å; Z=16. The final R value was 0.041 for 1924 unique reflections collected up to 2θ=70° with AgK α radiation. The modulation is displacive and sinusoidal in the (100) plane.
ESR Study of Silver Specks in Silver Halide Crystals
Authors: Sonoike Sanemi , Yoda Ryuuichi
Published: February 2005

A narrow single ESR line has been observed at room temperature in quenched silver halide crystals from the melt. The signal was eliminated when the samples were quenched in a chlorine atmosphere. It is attributed to the conduction electron spin resonance (CESR) of excess silver atoms decomposed from the residual silver compounds in the melt. The silver atom seems to be substituted for a halogen ion and behaves like a photographic sensitivity speck.
Optical Measurement of the Melt Depth During Pulsed Laser Irradiation
Authors: Nagahori Takeshi , Matsumoto Satoru
Published: February 2005

We propose a method of noncontact, nondestructive, and in situ evaluation of surface melting characteristics of semiconductors during pulsed laser irradiation. By regarding the melted layer caused by pulsed laser irradiation as thin films for optics, melting characteristics can be evaluated from time-resolved reflectivity measurements. We measure the surface melting characteristics of single crystal silicon caused by ArF excimer laser irradiation using this technique. From this experiment, it is found that maximum melt depth does not vary linearly with the incident energy density around the melting threshold.
Transport of e+ Beams from a Magnetic Field into a Non Magnetic Field
Authors: Sueoka Osamu , Yamazaki Mitsuhiro , Ito Yasuo
Published: February 2005

Transport of e+ (and e-) beams which are guided by a magnetic field to a non magnetic field was measured for the first time under several conditions. The transport efficiency when using an einzel lens was more than 80% for energy higher than 1.5 keV.
Room-Temperature Observation of Stark Ladder Formation in a Short-Period GaAs/AlAs Superlattice under an Electric Field
Authors: Fujiwara Kenzo
Published: February 2005

First room-temperature observation of the Wannier-Stark localization is reported in a short-period GaAs/AlAs superlattice with a 40-period of 3.2 nm GaAs/0.9 nm AlAs under an electric field by photocurrent spectroscopy. We show clear spectroscopic evidence for the evenly spaced Stark ladder spectra up to the 3rd order due to the Wannier-Stark localization which is in strong contrast to the usual quantum-confined Stark effects. Our results indicate an interesting possibility for application to a new-type electro-optic device based on the Wannier-Stark localization.
Modulation of Drain Current by Holes Generated by Impact Ionization in GaAs MESFET
Authors: Fujishiro Hiroki Inomata , Inokuchi Kazuyuki , Nishi Seiji , Sano Yoshiaki
Published: February 2005

A hole current generated by impact ionization in the channel at high drain voltages is measured using a GaAs MESFET with a conductive buried p layer (CBP-MESFET). The hole injection into the p layer beneath the channel is found to be the origin of the kink effect. A sidegating effect in the CBP-MESFET is also studied. A suppression of the sidegating effect by the negatively biased p layer is shown. An anomolous behavior in the sidegating effect at high drain voltages is observed; it may be related to the holes generated by impact ionization.
Preparation and Superconducting Properties of [Ln, Ce, (Ba1-xSrx)]8Cu6Oz (Ln=Nd, Sm and Eu)
Authors: Ichinose Ataru , Wada Takahiro , Yaegashi Yuji , Yamauchi Hisao , Tanaka Shoji
Published: February 2005

Superconductors of a new type, which belong to the [Ln1/2Ce1/6(Ba1-x
Sr
x
)1/3]8Cu6O
z
system, were prepared. The crystallographic structures of all the samples were tetragonal. The samples exhibited superconducting transitions in both electrical resistivity and ac magnetic susceptibility. The Meissner signal at 20 K of [Nd1/2Ce1/6(Ba0.625Sr0.375)1/3]8Cu6O18.45 (T
c
on=40 K) was about 13% of the perfect diamagnet. Not only the oxygen content, z, but also the substitution of Sr for Ba, x, as well as the ionic radius of the lanthanide element, Ln, in [Ln1/2Ce1/6(Ba1-x
Sr
x
)1/3]8Cu6O
z
were found to affect the superconducting properties.
High-Resolution Electron Microscopy and Electron Diffraction Study of an Incommensurate Bi1.8Sr1.5Ca1.5Cu2.2Ox Superconductor
Authors: Onozuka Takashi , Kajitani Tsuyoshi , Hirabayashi Makoto , Sato Hiroshi , Mitchell Terence E.
Published: February 2005

Weak contrast modulations with a long period of about 15 nm along [010] are observed in high-resolution lattice images of a Bi1.8Sr1.5Ca1.5Cu2.2O
x
superconductor. Contrast modulations with short periods, 4.5b

o
/2 (1.2 nm) and 5b

o
/2 (1.3 nm), along [010] are reproduced with a multislice computer simulation. Those contrast modulations as well as the intensities of incommensurate superlattice reflections are interpreted by a long period superlattice structure model consisting of alternative alignments of domains with the periods of 4.5b

o
and 5b

o
along [010].
Light Wavelength Dependence of Magneto-Optical Properties in Ultrathin Co/Pt and Co/Pd Multilayered Films
Authors: Hashimoto Shunichi , Ochiai Yoshitaka , Aso Koichi
Published: February 2005

Magneto-optical (MO) properties of ultrathin Co/Pt and Co/Pd multilayered films containing thin Co layers were investigated as a function of light wavelength of 390–850 nm in comparison with that of amorphous TbFeCo system. The Kerr rotation angle θK of these multilayers with 150 Å thickness was nearly constant (0.38–0.42 deg for Co/Pt and 0.24–0.28 deg for Co/Pd) in the visible region, and the θK of the Co/Pt system tended to increase in the ultraviolet region. On the contrary, the MO properties of TbFeCo films diminished linearly with decreasing light wavelength. The figure of merit √RθK of the Co/Pt films became 2.5 times larger than that of TbFeCo films at 400 nm. The ultrathin Co/Pt and Co/Pd multilayered films can be prominent material for higher-density MO recording using a shorter-wavelength laser.
Dynamic Response of Second Harmonic Generation in Ferroelectric Liquid Crystal
Authors: Ozaki Masanori , Yoshino Katsumi
Published: February 2005

The dynamic response of the second harmonic generation for a Q-switched Nd-YAG laser (wavelength: 1.064 µm) by the application of stepwise voltage has been studied in ferroelectric liquid crystal with large spontaneous polarization. It is found that the response consists of two components, that is, very fast (several hundred µs) and relatively slow (several hundred ms) responses. The fast and slow components of the response may correspond to the small modification and the main unwinding of the helical structure by the applied stepwise electric field, respectively.
Frequency Stabilization of Laser Diodes to the Cs-D2 Line with the Zeeman Modulation Method
Authors: Ikegami Takeshi , Ohshima Shin-ichi , Ohtsu Motoichi
Published: February 2005

The frequencies of AlGaAs laser diodes were stabilized to the F=4→F'=5 component of the Cs-D2 line with the Zeeman modulation method, in which the laser frequency remains unmodulated. Allan variance measurements were made on the beat note between two laser diodes thus stabilized and a frequency stability of 2.4×10-10 was obtained at an averaging time of 1s. By changing the dc magnetic field applied to the Cs cell, the frequency of the laser diodes could be tuned almost linearly in the range of -180 MHz to 180 MHz.
Enhancement- and Depletion-Mode GaAs MESFETs Grown by Laser-Assisted MOVPE
Authors: Ban Yuzaburoh , Ishizaki Mamoru , Asaka Tatsuya , Koyama Yoshihisa , Kukimoto Hiroshi
Published: February 2005

We have fabricated a pair of GaAs MESFETs operating in different modes, i.e., enhancement and depletion modes, on a single epitaxial wafer on the basis of laser-assisted metalorganic vapor phase epitaxy using tetramethylsilane as a photosensitive n-type dopant. The threshold voltages for an enhancement-mode MESFET fabricated on a laser-unirradiated part (n=3.5×1016 cm-3) and a depletion-mode MESFET on a laser-irradiated part (n
+=4.5×1017 cm-3) were +0.10 and -0.65 V, respectively. The drain current-voltage characteristics of two types of MESFETs showed a transconductance of about 13 mS/mm and a saturation drain current of about 250 µA.
Temperature Dependence of Flux Creep in High-Tc Superconductors
Authors: Fujiyoshi Takanori , Toko Kiyoshi , Matsushita Teruo , Yamafuji Kaoru
Published: February 2005

The normalized decay rate R of magnetization due to thermally activated flux creep is typically given by R≃k
B
T/U
c, where k
B is the Boltzmann constant, T is the absolute temperature and U
c is the effective pinning potential. Some observed data for high-T
c superconductors show that R increases with increasing T, while in other studies, R takes a peak at a certain temperature T
m below the critical temperature T
c, where T
m decreases with increasing external magnetic field. These temperature dependences of R are explained systematically on the basis of a recent theory of flux creep developed by the authors.
On the Formation of High-Tc Phase in Mo-Doped (Bi, Pb)2Sr2Ca2Cu3Oy Superconductors
Authors: Sato Ryuji , Komatsu Takayuki , Tamoto Nozomu , Sawada Kazuhiko , Matusita Kazumasa , Yamashita Tsutomu
Published: February 2005

We prepared superconducting Bi1.6-x
Pb0.4Mo
x
Sr2Ca2Cu3O
y
(x=0.05 and 0.1) and Bi1.6Pb0.4-x
Mo
x
Sr2Ca2Cu3O
y
(x=0.1, 0.2, 0.3 and 0.4) ceramics by the melt-quenching method and examind the effect of Mo addition on the superconducting properties. It was found that the formation of the high-T
c phase was largely enhanced by the coexistence of Pb and Mo elements. It was concluded that the lowering of the partial melting temperature at around 870°C caused by the addition of Mo element was very important for the formation of the high-T
c phase.
Preparation of a Ag-Doped Bi-Sr-Ca-Cu-O Bulk Sample by the Floating-Zone Method
Authors: Kubo Yukio , Michishita Kazuo , Shimizu Noriyuki , Higashida Yutaka , Yokoyama Hisanori , Hayami Yumi , Inukai Eikichi , Saji Akira , Kuroda Noboru , Yoshida Hiroshi
Published: February 2005

Bulk samples with nominal composition of Bi2Sr2CaCu2O
y
doped with 0, 10 and 20 weight % Ag were prepared by the floating-zone method at growth rates of 2 mm/h and 5 mm/h. Ag-doping seems to slightly enhance J
c, while annealing is very effective for J
c enhancement. From preliminary ac susceptibility measurements, the J
c enhancement by annealing is considered to be due to improvement of the weak link between superconducting grains.
The 10% Ag-doped sample grown at 2 mm/h possessed J
c of 5360 A/cm2 at 77 K under zero magnetic field after annealing.
X-Ray Photoemission Spectroscopy of Nd2-xCexCuO4-y and La2-xSrxCuO4
Authors: Ishii Hiroyoshi , Koshizawa Takehito , Kataura Hiromichi , Hanyu Takaaki , Takai Hiroyuki , Mizoguchi Kenji , Kume Kiyoshi , Shiozaki Ikuyo , Yamaguchi Shigeo
Published: February 2005

We have measured the Cu 2p and O 1s X-ray photoemission spectra of the high-T
c superconductors Nd2-x
Ce
x
CuO4-y
and La2-x
Sr
x
CuO4, and the copper oxides CuO and Cu2O. The Cu 2p spectra of superconductors show features similar to those of CuO with divalent Cu ions. For Nd2-x
Ce
x
CuO4-y
, the intensity ratio of the satellite to the main peaks decreases with increasing Ce content. The O 1s spectra exhibit a single-peaked structure and are insensitive to whether either electron or hole is doped.
Contact Resistance and V-I Characteristics in a Ag-Doped Bi-Sr-Ca-Cu-O Superconductor
Authors: Shimizu Noriyuki , Michishita Kazuo , Higashida Yutaka , Yokoyama Hisanori , Hayami Yumi , Kubo Yukio , Inukai Eikichi , Saji Akira , Kuroda Noboru , Yoshida Hiroshi
Published: February 2005

Contact resistance and V-I characteristics were investigated in Ag-doped and undoped Bi-Sr-Ca-Cu-O bulk samples prepared by the floating-zone method. In undoped samples, with increasing current pulse width, rapidity of voltage rise in V-I characteristics increases and J
c decreases. The contact resistance is nonohmic and temperature dependence is semiconductorlike. In a Ag-doped sample, rapidity of voltage rise and J
c are not influenced by pulse width, and deviation of J
c among samples is small. The ohmic contact resistance has metallike temperature dependence, and its value is less than 1/500 of that in an undoped sample.
Preparation of Superconducting (Bi, Pb)-Sr-Ca-Cu Oxide Tapes with a Highly Oriented Structure by the Solidification Method
Authors: Matsuzaki Kunio , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

Composite tapes consisting of Au and superconducting Bi-Sr-Ca-Cu or Bi-Pb-Sr-Ca-Cu oxide with a pseudotetragonal structure were prepared by annealing the oxide phase which was slowly solidified on the Au tape. The oxide phase has a highly oriented structure, and the c plane lies parallel to the surface of the tape. The tapes were found to exhibit zero resistance at temperatures above 100 K as well as good bending flexibility. The critical current density (J
c) at 77 K in the absence of applied field is 96 A/cm2 for the BiSrCaCu2O
y
-Au tape and 108 A/cm2 for the Pb0.2BiSrCaCu1.5O
y
-Au tape.
Scattering Matrix Theory of Resonant Tunneling
Authors: Zohta Yasuhito
Published: February 2005

Scattering matrix formulation of resonant tunneling is derived for a one dimensional double barrier structure. This formulation is more accurate than the path integral formulation developed by the author and is usable for device simulation. The point in which it most differs from the existing methods is that the effect of scattering is taken into account by cutting off the number of reflections in the well so that they become finite.
Field-Effect Transistors using Boron-Doped Diamond Epitaxial Films
Authors: Shiomi Hiromu , Nishibayashi Yoshiki , Fujimori Naoji
Published: February 2005

Metal-semiconductor field-effect transistors (MESFET's) have been fabricated on a boron-doped diamond epitaxial film. This is the first report of a planar type transistor using a diamond film.
Synchrotron Radiation Photoelectron Spectroscopy of High-Tc Superconductor Bi-Sr-Ca-Cu-O Single Crystals
Authors: Maeda Fumihiko , Kawamura Tomoaki , Oshima Masaharu , Hidaka Yoshikazu , Yamaji Akihiko
Published: February 2005

Photoelectron measurements made on the high-T
c superconductor single crystals of Bi2(Sr, Ca)3Cu2O
x
using synchrotron radiation of 35–120 eV revealed a valence band satellite due to the two-hole bound state, which indicated considerable large intra-atomic Coulomb energy between Cu-3d electrons. The density of states on the Fermi level was clearly observed. This feature is quite different from those of the La-Sr-Cu-O and Y-Ba-Cu-O systems.
Evidence of Sr-Deficiency in Bi2Sr2-αCa1Cu2O8 and Preparation of Stoichiometric Semiconducting Bi2Sr2Ca1Cu2O8
Authors: Nagano Hiroshi , Liang Ruixing , Matsunaga Yoshinori , Sugiyama Masakazu , Itoh Mitsuru , Nakamura Tetsurō
Published: February 2005

When samples with the starting composition of Bi:Sr:Ca:Cu=2:2:1:2 were heat-treated under the oxygen partial pressure range from 1 to 0.0001 atm at 820°C, at least three different multiphase regions with the following component phases appeared: Bi2Sr2Cu1O
y
+Sr-rich Bi-Sr-Ca-Cu-O+Sr-deficient Bi2Sr2-αCa1Cu2O
x
, stoichiometric Bi2Sr2Ca1Cu2O8, and Bi2Sr2Ca1O6+Cu2O. The amount of Sr-deficiency in the Bi2Sr2-αCa1Cu2O8 homogenized sample with the stoichiometric composition of Bi2Sr2Ca1Cu2O8 exhibited semiconductivity.
Influence of Intermediate Pressing on Superconducting Characteristics in Bi-Pb-Sr-Ca-Cu-O System
Authors: Ito Atsushi , Matsuda Motohide , Iwai Yutaka , Ishii Mamoru , Takata Masasuke , Yamashita Tsutomu , Koinuma Hideomi
Published: February 2005

The influence of intermediate pressing after the initial sintering on the superconducting characteristics in the Bi-Pb-Sr-Ca-Cu-O system was investigated. Though the sample prepared by the conventional process had a porous structure with a T
c,zero of 105 K, an as-pressed sample prepared by intermediate pressing after the initial sintering had relatively dense structure and its superconducting transition became very broad. However, further sintering caused significant improvements in the superconducting characteristics.
Analytical Electron Microscopy of High-Tc Superconductors in the (Bi, Pb)-Ca-Sr-Cu-O System
Authors: Shindo Daisuke , Sato Hiroshi , Liedl Gerald L. , Hiraga Kenji , Kobayashi Norio , Hirabayashi Makoto , Muto Yoshio
Published: February 2005

Superconductors in the Bi-Ca-Sr-Cu-O system containing a small amount of Pb were investigated by analytical electron microscopy as well as high-resolution electron microscopy. X-ray spectroscopy analysis showed that most of grains in the samples contain approximately the same amount of Pb, and the compositions of the grains with the low-T
c (60 K) phase correspond to (Bi, Pb)1.1(Ca, Sr)1.4Cu1.0O
x
. The compositions of the samples containing high-T
c phase differ from grain to grain but indicate higher Cu atomic fraction than that of the low-T
c phase. High resolution electron microscope images directly reveal the modulated structure along the [010] direction with an incommensurate period which is the same as that observed in Bi-Ca-Sr-Cu-O. Electron energy loss spectra were also investigated by means of parallel detection system. The position and shape of the strong peak above the threshold at the oxygen K-edge were discussed relative to data for YBa2Cu3O
x
.
Chevron Layer Structure in the Smectic A Phase of 8CB
Authors: Takanishi Yoichi , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

The smectic A layer structure of a homogeneously aligned 8CB liquid crystal (25 µm in thickness) has been studied by X-ray diffraction analysis. Contrary to the common recognition, it is found, for the first time, that the local layer structure of this type of cell changes to a chevron layer structure from a book-shelf structure, as the temperature decreases away from the N-SA phase transition point. The formation of the chevron layer structure is also recognized by the characteristic defects: zig-zag defects appear as a boundary of two opposite chevron structures with focal conics.
Dependence of Gettering Efficiency on Metal Impurities
Authors: Miyazaki Morimasa , Sano Masakazu , Sadamitsu Shinsuke , Sumita Shigeo , Fujino Nobukatsu , Shiraiwa Toshio
Published: February 2005

The dependence of gettering efficiency on metal impurities was investigated by means of an intentional contaminating method using Ni or Fe and the MOS C-t method with an eye to using gettering techniques appropriately. The results showed that Ni is easily gettered but Fe is not. Therefore, as a second step, the condition improving gettering efficiency for Fe was investigated. It was consequently found that adding heat treatment at low temperature to the final heat cycle is effective for gettering of Fe.
Structural and Electrical Properties of P- and B-Doped Polycrystalline Silicon by Plasma-Enhanced CVD at 700°C
Authors: Hasegawa Seiichi , Morita Minoru , Kurata Yoshihiro
Published: February 2005

Undoped, P- and B-doped polycrystalline Si films were prepared on a fused quartz substrate at 700°C by low-pressure CVD (LPCVD) and plasma-enhanced CVD (PECVD) using the same fabrication system. The effects of plasma supply on the structural and electrical properties were investigated. All of the PECVD films show a strong < 110 > texture, in contrast with LPCVD films with a nearly random texture. Plasma supply also has the effect of essentially smoothing the surface, independent of the doping level of either dopant, and for improvement of the P- and B-doping efficiency in an intermediate doping range.
Electroluminescence in an Oxygen-Doped ZnSe p-n Junction Grown by Molecular Beam Epitaxy
Authors: Akimoto Katsuhiro , Miyajima Takao , Mori Yoshifumi
Published: February 2005

Blue electroluminescence has been obtained from ZnSe p-n junctions. ZnSe films were grown on n-type GaAs(100) substrates by molecular beam epitaxy. The dopants used for n-and p-type ZnSe were Ga and O, respectively. The electron-beam-induced current strongly suggests the formation of a p-n junction. The built-in Potential of the p-n junction and carrier concentration of p-type ZnSe layer estimated from the capacitance-voltage relation were about 2.3 V and 1.2×1016cm-3, respectively. The electroluminescence spectra from the p-n junction were dominated by band-edge emissions of 466 nm at room temperature and 446 nm at 77 K.
ESR Study of BiSrCaCu2Ox
Authors: Tagaya Kimihito
Published: February 2005

ESR measurements were performed for BiSrCaCu2O
x
ceramics over the temperature range from 77 K to room temperature. From the broad microwave absorption, the Meissner effect was observed for a superconducting specimen, and the lower critical field of the high-T
c phase was determined to be 22 Oe at 77 K. After the specimen was heat-treated at 950°C in air, the Meissner effect became weak, and an ESR signal was observed due to precipitated CuO particles, which exhibited a superparamagnetism. A broad absorption of Cu2O was also observed for a specimen heated at 1050°C in air and then quenched.
Observation of the High-Tc Phase and Determination of the Pb Position in a Bi-Pb-Sr-Ca-Cu Oxide Superconductor
Authors: Nobumasa Hitoshi , Arima Takahisa , Shimizu Kazuharu , Otsuka Yuji , Murata Yukio , Kawai Tomoji
Published: February 2005

The high-T
c phase of a Bi-Pb-Sr-Ca-Cu oxide superconductor was observed directly by high-resolution transmission electron microscopy (HREM), and the atomic positions of Pb in the crystal were determined by high-resolution analytical electron microscopy (HRAEM) with a high spatial resolution 17 Å using a probe 5 to 10 Å in diameter. The HREM observation revealed that the crystal consisted solely of a triple Cu-O layered structure with c/2=18 Å and without any intergrowth, and that the crystal structure was modulated along the b-axis. The HRAEM indicated that the Pb atoms were located in the Bi-O layers with an atomic ratio of Pb/Bi∼0.1.
Superspace Group Analysis of the Modulated Structure in Superconductor Bi-Sr-Ca-Cu-O
Authors: Yamamoto Naoki , Hirotsu Yoshihiko , Nakamura Yoshio , Nagakura Sigemaro
Published: February 2005

The superspace group of the modulated structure in the superconducting Bi-Sr-Ca-Cu-O oxide has been derived from the systematic extinction in the electron diffraction patterns, which was found to beN11̄1BbmborN111Bb2b. General properties of the modulation waves for the atomic displacements and occupation probabilities are deduced from the symmetries of the superspace group. A model of the modulated structure based on these properties is proposed with reference to high resolution electron micrographs of the crystal.
The Phase Change Due to Oxygen Content in the LnBa2Cu3Oy Compound Systems (Ln=Tm, Gd, Sm)
Authors: Kogachi Mineo , Nakanishi Shigemitsu , Nakahigashi Kiyotaka , Sasakura Hiroyuki , Minamigawa Shinnosuke , Fukuoka Nobuo , Yanase Akira
Published: February 2005

The phase change due to oxygen content y (7>y>6) was investigated for TmBa2Cu3O
y
(TBC), GdBa2Cu3O
y
(GBC) and SmBa2Cu3O
y
(SBC) by means of X-ray diffraction and electrical resistivity. The phase boundary between orthorhombic and tetragonal phases moved toward the oxygen-rich side when the system changed as TBC→YBa2Cu3O
y
(YBC)→GBC→SBC. The plateau in the critical temperature T
c was observed in the intermediate region of 6.7>y>6.4 for each system, supporting the existence of an orthorhombic-II phase. It seemed to exhibit a system dependence, i.e., a decrease in T
c in the order of TBC, YBC, GBC and SBC.
High Pressure Hot-Pressing of Y1Ba2Cu3O7-δ Superconductor
Authors: Kawahara Nobuaki , Enami Hiroyoshi , Kitoh Yasuo , Shinohara Toshiyuki , Kawabata Sanemasa , Hoshizaki Hiroki , Matsumuro Akihito , Imura Toru
Published: February 2005

An almost theoretical density of Y1Ba2Cu3O7-δ was achieved under a high pressure of 5.4 GPa. While the pressed sample showed a semiconducting behaviour, the postannealed sample showed a superconducting transition with T
c, onset=92 K, T
c, end=90 K. The best critical current density, J
c at 77 K was 1650 A/cm2. The crystal structure of Y1Ba2Cu3O7-δ was distorted by the high pressure but recovered through annealing.
Critical Current Density and Its Hysteresis in Magnetic Field for Ba-Y-Cu-O Films Prepared by a Sputtering Technique
Authors: Morita Hiroaki , Watanabe Kazuo , Murakami Yoshitake , Koyanagi Yosuke , Noto Koshichi , Fujimori Hiroyasu , Muto Yoshio
Published: February 2005

A considerably large transport critical current density J
c (1.2×105 A/cm2 at 4.2 K and 15 T) was observed for the superconducting Ba-Y-Cu-O thin films prepared by an rf sputtering method. In association with such a large J
c, the hysteresis of J
c against the applied magnetic field was smaller compared to that in bulk samples prepared by a solid phase reaction method. It was considered that a fairly smooth morphology of grain boundaries in the thin films improved superconducting properties. The hysteresis of J
c was discussed on the basis of the weak link model.
Lattice Parameters and Surface Morphology of the High-Tc Phase in Bi-Sr-Ca-Cu-O Superconducting Thin Films
Authors: Kozono Yuzoo , Ohno Toshiyuki , Kasai Masahiro , Hanazono Masanobu , Sugita Yutaka
Published: February 2005

Bi-Sr-Ca-Cu-O thin films with different T
c values in the range from 110 K to 84 K were prepared on MgO(100) crystal by an rf-magnetron sputtering technology. The volume ratio of the high-T
c phase, its lattice parameters and the surface morphology for these films were investigated. T
c became higher as the c- and a-axes became shorter. The lattice parameters of the film with T
c=110 K were c=37.15 Å and a=5.41 Å, which were the same as for bulk ceramics with T
c=110 K. The grain size was larger for the higher-T
c films.
Annealing Study of Bi-Sr-Ca-Cu-O Superconducting Thin Film
Authors: Ikeda Kazuto , Gotoh Kotaro , Ihara Masaru , Ozeki Masashi
Published: February 2005

We studied the postannealing conditions needed to make the 110 K phase in Bi-Sr-Ca-Cu-O superconducting thin film deposited on (001) single-crystal MgO substrates by rf magnetron sputtering. We used X-ray diffraction to estimate the amount of 110 K phase in the film. We found that the film included a large 110 K phase at about 840°C in 7–8% oxygen/helium flow and that high-speed cooling can suppress the 80 K phase formation. By comparing films made with different cooling rates, we conclude that the tail of the temperature dependence curve of the electrical resistance does not depend on the other superconducting phases whose c-axes are perpendicular to the sbstrate surface.
Magneto-Optical Properties in Ultrathin Co/Pd and Co/Pt Multilayer Films
Authors: Ochiai Yoshitaka , Hashimoto Shunichi , Aso Koichi
Published: February 2005

Co/Pd and Co/Pt multilayer films were prepared by magnetron-type sputtering and their magnetic properties were characterized by a polar Kerr loop tracer. Both multilayer films had perpendicular magnetic anisotropy when the Co layer became ≦10 Å. It was found that the magneto-optical and magnetic properties were significantly affected by the film thickness. The Kerr rotation angle θk was enhanced at the film thickness t\lesssim500 Å and the Kerr remanence to saturation ratio became θkr/θk=1 at t≦200 Å. In the Co/Pd system, the coercive force was influenced by the sputtering gas pressure. Simultaneous enhancement in θk and θkr/θk is assumed to originate from the different natures.
Linearly Polarized Operation of PANDA-Type Nd-Doped Fiber Lasers
Authors: Shimizu Makoto , Horiguchi Masaharu
Published: February 2005

Linearly polarized operation is demonstrated for PANDA-type Nd-doped fiber lasers. Using the stress-induced bending-loss difference between two orthogonal modes in the PANDA fiber, we achieve extinction ratio of more than 31 dB and a slope efficiency of 32%.
Buried Heterostructure GaAs/GaAlAs Distributed Bragg Reflector Surface Emitting Laser with Very Low Threshold (5.2 mA) under Room Temperature CW Conditions
Authors: Ibaraki Akira , Kawashima Kenji , Furusawa Kohtaro , Ishikawa Tohru , Yamaguchi Takao , Niina Tatsuhiko
Published: February 2005

We would like to report on the performance of buried heterostructure (BH) GaAs/Ga0.65Al0.35As surface emitting (SE) lasers with p-type Ga0.9Al0.1As/Ga0.4Al0.6As and SiO2/TiO2 multilayer Bragg reflectors (MBR) under room temperature CW conditins. The buried heterostructure was formed by a selective LPE growth technique with a Ga0.55Al0.45As mask instead of the conventional SiO2 mask. The GaAlAs mask was very useful for forming uniformly small active regions of about 5 µm in diameter. Under room temperature CW conditions, the threshold current was 5.2 mA. The external differential quantum efficiency was about 16% and more than 0.6 mW of output power was obtained. The lasing wavelength was about 897 nm.
Electric Field Effects on Faraday Rotation of Cd1-xMnxTe Films Prepared by Ionized Cluster Beams
Authors: Koyanagi Tsuyoshi , Yamano Koji , Sota Tetsuo , Nakamura Kimio , Matsubara Kakuei
Published: February 2005

Effects of an electric field on the Faraday rotation of Cd1-x
Mn
x
Te films, prepared by ionized cluster beams, have been investigated. A marked change in the Faraday rotation was observed near the band gap energy under an applied electric field perpendicular to the film plane. The maximum change Δ
V in the Verdet constant obtained for a Cd0.49Mn0.51Te film was of the order of 0.22°/cmG at an electric field of 174 kV/cm. It was found that this effect could be attributed to the electric field effects on optical absorption by excitons.
Surface Analysis of Single Crystals in the Bi-Sr-Ca-Cu-O System by Low-Energy Electron Diffraction and Auger Electron Spectroscopy
Authors: Nakanishi Shigemitsu , Fukuoka Nobuo , Nakahigashi Kiyotaka , Kogachi Mineo , Sasakura Hiroyuki , Minamigawa Shinnosuke , Yanase Akira
Published: February 2005

The cleaved surfaces of low-T
c-phase single crystals in the Bi-Sr-Ca-Cu-O system were investigated by means of the LEED (low-energy electron diffraction) and AES (Auger electron spectroscopy) techniques. The LEED patterns from the cleaved surfaces exhibited a modulated structure with a period of about 4.8a, as expected from the modulation in the bulk crystals. The incident angular dependence of the Auger signal intensity revealed that the crystals were exactly cleaved between the Bi double layers. Through detailed analysis of the dependence based on a model calculation, it was found that oxygen was absent or strongly deficient on the cleaved surfaces. It was also suggested that the weak bond of Bi-O is the principal reason for the cleavability between the Bi double layers.
HIPped High Density Bi-(Pb)-Sr-Ca-Cu-O Superconductors Produced without Any Additional Treatment
Authors: Seino Hiroshi , Ishizaki Kozo , Takata Masasuke
Published: February 2005

Superconducting ceramics (BiSrCaCu2O
x
and BiPb
y
SrCaCu2O
x
) were directly obtained for the first time by a hot isostatic press (HIP) densification without any additional treatment. The ceramics obtained from BiSrCaCu2O
x
were 85 K superconductors and the ones obtained from BiPb
y
SrCaCu2O
x
had a high-T
c phase, which was not observed before the HIP process. The HIPped BiSrCaCu2O
x
samples were densified to 5600 kg/m3, and with PbO additions, the density was around 6000 kg/m3. All the conventionally processed samples had a lower T
c,zero of 65 K and lower densities of about 4600 kg/m3. A remarkable improvement in crystallinity and sharper superconducting transition were achieved through the HIP densification process without any additional treatment.
ESR and Nonresonant Microwave Absorption in a High-TcSuperconductor of the Tl-Ba-Ca-Cu-O System
Authors: Hayashi Yoshikazu , Fukui Minoru , Fujita Tetsuo , Shibayama Hideo , Iwahashi Katsutoshi , Adachi Kengo
Published: February 2005

Electron spin resonance (ESR) in a high-Tcsuperconductor of the Tl-Ba-Ca-Cu-O system is observed. Two components of ESR exist. Above 140 K, the intensity of the ESR signal increases as the temperature decreases. Below 140 K, the signal intensity decreases as the temperature decreases and disappears atTc(124 K), clearly indicating the relation to the superconductivity. Nonresonant absorption is greatly enhanced atTc. BelowTc, an abrupt change in the derivative curve of the nonresonant microwave absorption occurs at the magnetic field corresponding to the lower critical field.
Superconductivity in Nd-Ce-Cu-O Thin Films
Authors: Hayashi Shigenori , Adachi Hideaki , Setsune Kentaro , Hirao Takashi , Wasa Kiyotaka
Published: February 2005

Highly oriented superconducting Nd-Ce-Cu-O thin films have been grown on (100) SrTiO3 substrates with the c-axis nominal to the substrate by a sputtering method and postannealing. After annealing in a vacuum, the films showed superconductivity with the onset temperature of 20 K and a transition width of 2 K. It was confirmed by Hall effect measurements that the charge carriers in the normal state are electrons.
Quantum-Confined Stark Effect in a Parabolic-Potential Quantum Well
Authors: Ishikawa Takuya , Nishimura Shinji , Tada Kunio
Published: February 2005

Quantum-confined Stark effect in parabolic quantum well (PQW) has been analyzed both analytically and numerically. Analytical studies have revealed that the fundamental absorption edge shift in PQWs is proportional to the square of the well width, and that the Stark shift in PQWs is independent of the particle mass. From numerical calculations, it has been confirmed that PQW structure enables us more easily than rectangular quantum well to obtain the absorption-type optical waveguide switches whose characteristics are nearly polarization-independent, and that PQW is also advantageous if we intend to obtain the polarization-independent changes in the refractive index with low field and over a wide wavelength region. In addition, an equivalent PQW structure has been fabricated, and the mass-independent Stark shift of the PQW has been observed for the first time.
Deposition of Ga, Al and As Layers by Laser-Assisted Decomposition of Trimethylgallium, Trimethylaluminum and Arsine
Authors: Ban Yuzaburoh , Komatsu Hiroshi , Takechi Masaru , Ishizaki Mamoru , Kukimoto Hiroshi
Published: February 2005

We have investigated the substrate temperature dependence of deposition rates for Ga, Al and As layers formed on fused quartz (Suprasil) substrates by ArF excimer laser-assisted chemical vapor deposition using trimethylgallium, trimethylaluminum and arsine as source materials, respectively. The deposition rates for Ga and Al were independent of substrate temperature in the range from 100°C to 400°C, and then increased with substrate temperature above 400°C. On the other hand, the As deposition rate decreased dramatically with increasing substrate temperature up to 300°C. The result of As deposition can be explained qualitatively by three competing processes of the laser decomposition of arsine and laser and/or thermal desorptions of the As atom.
Laser-Induced Polymerization of Surface Adsorbed Molecules
Authors: Kizaki Yoshimi , Taguchi Toshiyuki , Yamazaki Satoshi
Published: February 2005

The controllability of the chemical composition of acrylic compounds was investigated in ultrathin polymerized films by using a polymerization processin vacuowith a vacuum UV excimer laser. Four different acrylic compounds were polymerized by this process. The analysis of X-ray photoelectron spectroscopy showed that the chemical compositions of polymer film from ethylacrylate were well-preserved monomer compositions. The insulation characteristics of the ultrathin films obtained from the optimized conditions were found to be sufficient for producing a MIS device on n-type GaAs substrates.
Computer Analysis of Megagauss Field Generation by Condenser Bank Discharge
Authors: Miura Noboru , Nakao Koichi
Published: February 2005

Experiments on the generation of very high magnetic fields in the megagauss range (>100 T) by use of a large current from condenser banks are analysed by a computer simulation. The analysis is performed for the electromagnetic flux compression with both the θ-pinch and z-pinch configuration as well as the single-turn coil technique. The distribution of the current and temperature of the liner or the coil is appropriately treated by a 2-dimensional analysis dividing the cross-section into many mesh sections. The deformation of the liner during the implosion is calculated by a finite-element method. A good agreement between the calculation and recent experiments was obtained.
Penetration of Hypervelocity Projectiles into Aluminum Multisheet Stacks
Authors: Fujiwara Akira , Kadono Toshihiko
Published: February 2005

Aluminum multisheet stackes were penetrated by nylon projectiles with a velocity up to about 4.4 km/s. Penetration depth, size of the hole produced on each sheet of the stacks, and recovery rate of the projectiles were investgated as a function of the impact velocity and the spacing between the sheets, and for some of these quantities, empirical formulae are provided.
Crystal Growth Process of Rb-Doped Iron Garnet Films for M-O Recording Prepared by Pyrolysis
Authors: Nakagawa Katsuji , Odagawa Kenji , Itoh Akiyoshi
Published: February 2005

The crystal growth process of nondoped and Rb-doped Bi-iron garnet films prepared by pyrolysis on glass substrates was investigated. The growth processes were observed with a differential interference microscope. Crystal domains appearing at the early stage of the annealing were fused to each other with the progress of the annealing. Rb-doped films were much more smooth and uniform than the nondoped films. It is concluded that the contrast of light intensity observed by DIM was not caused by the surface roughness but was caused by the inhomogeneity of the refractive index. The media noise and writing noise level could be decreased in the Rb-doped films because of their improved homogeneity.
Effect of Oxygen Doping into SiBN Ternary Film
Authors: Maeda Masahiko
Published: February 2005

Oxygen-doped SiBN films are proposed. The effect of oxygen doping is discussed by considering the bonding configuration of oxygen atoms in SiBN films evaluated using infrared absorption spectroscopy and X-ray photoelectron spectroscopy. While SiBN film is characterized as a material with a low dielectric constant, a lower dielectric constant is obtained by oxygen doping into SiBN film in the [O]/2[Si]<1 region. In this region, oxygen atoms preferentially combine with Si atoms, and lower polarizability Si-O bonds are formed in the films in place of higher polarizability Si-N bonds. However, in the [O]/2[Si]>1 region, the dielectric constant of films increases because oxygen atoms combine with B atoms and polar B-O bonds are formed in the film. The breakdown strength of oxygen-doped SiBN films becomes higher with a decrease in the films' dielectric constant.
Control of the Two-Electron-Temperature Plasma Parameter in a DP Device
Authors: Yamazumi Tomiya , Ikezawa Shunjiro
Published: February 2005

A two-electron-temperature plasma is observed in a double-plasma device when the space potential approaches the potential of the cathode filaments. The densities of the hot and cold electrons (N
eh and N
ec) are controlled by the target discharge current I
t and target filament current I
Ft. When I
t increases, N
eh increases. When I
Ft increases, N
ec increases. The ratio of the density of the hot to the cold electronsm, N (=N
eh/N
ec), can be controlled: when I
t increases, N increases from 0.8 up to 5.0, and when I
Ft increases, N decreases from 1.1 to 0.25. The hot and cold electron temperatures T
h and T
c are kept almost constant at 3.5∼6.0 eV and 1.0 eV, respectively.
Calibration Source for Electron Cyclotron Emission Measurements
Authors: Kawahata Kazuo , Sakamoto Mizuki , Fujita Junji , Matsuo Hiroshi , Sakai Kiyomi
Published: February 2005

A high-temperature radiation source has been developed for the absolute calibration of diagnostic instruments for measuring electron cyclotron emission from high-temperature plasmas. The source has a radiation area of φ 150 mm and can be heated up to 500°C. The measured emissivity of the source is close to unity in the spectral region between 200 and 500 GHz. The grating polychromator has been calibrated using the radiation source developed. The obtained temperatures agree with those by the pulse height analysis of soft X-rays and Thomson scattering measurement within 10%.
Ion-Implanted Diamond Tip for a Scanning Tunneling Microscope
Authors: Kaneko Reizo , Oguchi Shigemitu
Published: February 2005

An ion-implanted diamond tip sharpened to a radius of about 100 nm has sufficient conductivity for scanning tunneling microscopy. This tip can be used repeatedly even if it contacts the sample surface. Because the radius of the tip can be easily checked and does not show much wear from repeated usage, the relation of the tip radius to image resolution can be estimated.
Spectroscopic Study on a Discharge Plasma of MOCVD Source Gases for High-Tc Superconducting Films
Authors: Harima Hiroshi , Ohnishi Hiroshi , Hanaoka Ken-ichi , Tachibana Kunihide , Kobayashi Minoru , Hoshinouchi Susumu
Published: February 2005

Optical emission spectra from a glow-discharge plasma in the vapors of β-diketonate chelates of Ba, Y and Cu element have been measured. They show great changes depending on the temperature of the source-gas oven. In the case of Ba(DPM)2, for example, intensity of the Ba+ emission lines increases drastically at above 220°C, when compared to neutral lines. Referring to the data of thermal analysis and IR absorption experiment, this corresponds to the development of decomposition of the source material. The present experiment opens a future possibility of optical diagnostics to determine the optimum gas feeding condition in the preparation of high-T
c superconducting films by the MOCVD technique.
Effect of Substrate Temperature on the Photovoltaic Properties of a CdS/CdTe Solar Cell
Authors: Uda Hiroshi , Ikegami Seiji , Sonomura Hajimu
Published: February 2005

Structural and electrical properties of CdTe thin films prepared by the conventional vacuum evaporation method were studied. Photovoltaic properties of thin-film CdS (chemical-solution-deposited)/CdTe (vacuum-evaporated) solar cells were also investigated. The crystal structure of CdTe films deposited on the CdS films at the substrate temperature of 300∼520°C was of the zincblende type with a preferential orientation of the (111) plane parallel to the substrate. The dark resistivity of the CdTe films deposited on the glass substrates was about 107 Ωcm. Illumination caused the resistivity decrease of the films by about two orders of magnitude. The conversion efficiency of the CdS/CdTe solar cells increased with increasing substrate temperature. The present thin-film CdS/CdTe solar cell showed a conversion efficiency of greater than 5%.