bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Some Additives on Thermoelectric Properties of FeSi2 Thin Films
Authors: Komabayashi Masashi , Ido Ken-ichi Hijikata
Published: February 2005

Effects of some additives (V, Cr, Mn, Co, Ni, Pd, Pt) on thermoelectric properties of FeSi2 thin films were studied. V, Cr or Mn-doped FeSi2 films were of p-type semiconductor and Co, Ni, Pd and Pt-doped FeSi2 films of n-type semiconductor. It was indicated that V or Cr are more suitable additives in thermoelectric properties of p-type FeSi2 than Mn and that Pt is superior to other additives in thermoelectric properties of n-type FeSi2.
Effect of Substrate Off-Orientation on GaAs/CaF2/Si(111) Structure with Rotational Twin
Authors: Mizukami Hiroyuki , Kazuo Tsutsui Kazuo Tsutsui , Seijiro Furukawa Seijiro Furukawa
Published: February 2005

The effect of off-orientation of substrate was investigated to improve the surface morphology and crystallinity of CaF2/Si(111) and GaAs/CaF2/Si(111) structures which were grown by molecular beam epitaxy. It was found that drastic improvement of surface morphology of the CaF2 films and the GaAs films was observed by using Si(111) substrates off-oriented toward not [110] but the [001] direction. Hall measurements showed that electrical properties of the GaAs films were also improved by using these substrates. This report pointed out that selection of the direction toward which the substrate is off-oriented is very important for growth of the GaAs/CaF2/Si(111) structure which has a rotational twin, the so-called “type-B” epitaxial relation.
Experiment and Analysis on High-Electric-Field Transport in Epitaxial YBaCuO Thin Films
Authors: Sakuta Ken , Asano Katunori , Arisaka Syuji , Ken-ichi Matsui Ken-ichi Matsui , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

Hot carrier transport in epitaxial (001)Y1Ba2Cu3O
y
thin films has been closely investigated under application of pulsed high electric field. The current-vs-field curves of the normal conduction for both the semiconducting and superconducting phase films exhibited strong nonlinearity as the field increased. The nonlinearity of the dynamic resistance measured at 50-100 MHz was exaggerated much more. These phenomena were analyzed through analogy to the high-field transport in semiconductors. On the basis of the dominant phonon scattering, the results implied that the Y1Ba2Cu3O
y
carrier localizes in a thin layer and has two-dimensional motion, and that the deduced effective mass is heavier than 2m
0 but less than 5m
0, where m
0 is the free electron mass.
Evalution of Practical Application Characteristics for New Magneto-Optical Recording Medium MnBiAlSi
Authors: Min Yang Ke , Wang Yin Jun Wang Yin Jun , Wang Huan Yuan Wang Huan Yuan
Published: February 2005

Quasi-dynamic thermomagnetic write/read/erase and lifetime experiments on new magneto-optical recording material MnBiAlSi film which has a singnificant Kerr rotation angle have been achieved for the first time and the characteristics with practical application worth have been also initially obtained. As a result, it is a promising material for the magneto-optical disc use.
Spontaneous Emission in a Very Short Optical Cavity with Plane-Parallel Dielectric Mirrors
Authors: Ujihara Kikuo , Nakamura Atsushi , Osamu Manba Osamu Manba , Xiao-Ping Feng Xiao-Ping Feng
Published: February 2005

A detailed account of the calculation on the spontaneous emission rate in a very short optical cavity with plane-parallel dielectric mirrors is given. A cavity model consisting of a pair of plane dielectric slabs is used. Guided modes as well as outgoing modes are considered. The emission rate from a two-level atom is calculated under quantum-mechanical perturbation approximation. The enhancement factor for the rate is found to be of the order of unity except for extremely short cavities. The concept of quasimodes in a very short cavity and their effective area are discussed in relation to the enhancement factor. The coupling ratios into various quasimodes are derived.
Effects of BaTiO3 Self-Pumped Phase-Conjugation in 400-m Atmospheric Optical Path
Authors: Tokuyuki Honda Tokuyuki Honda , Hirokazu Matsumoto Hirokazu Matsumoto
Published: February 2005

A 400-m optical path is constructed through the atmosphere using a self-pumped phase-conjugate mirror (PCM) of a photorefractive BaTiO3 crystal as a retroreflector. Intensity fluctuations of laser beams are reduced by 10 dB compared to the case of a conventional plane reflecting mirror. Moreover, some additional advantages of using the PCM in such a long-optical-path system are discussed.
Laser Properties of Nonlinear Optical Benzal Barbituric Acid Crystals
Authors: Kondo Koichi , Fukutome Masato , Ohnishi Noriaki , Aso Hideyuki , Kitaoka Yasuo , Sasaki Takatomo
Published: February 2005

A nonlinear optical crystal, p-methylbenzal-1,3-dimethylbarbituric acid, has been grown in benzene by a temperature depression method into a large single crystal (10×16×27 mm3). The cut-off wavelength is 460 nm, and the effective nonlinear optical coefficient d
eff of type I for second harmonic generation (SHG) is 8.0 pm/v.
Optical Modelling of a Black Copper Selective Surface
Authors: Purnima Richharia Purnima Richharia , K. L. Chopra K. L. Chopra
Published: February 2005

This paper presents theoretically computed reflectance spectra of a chemically converted textured black copper selective surface. The computation has been carried out using a simple structural model which is based on the experimental evidences. The desired effective dielectric permittivity of this multiphase composite film has been achieved using the effective medium concept. The computed effective dielectric permittivity obtained along with the multilayer configuration using a matrix approach shows satisfactory agreement between the theoretically computed and the experimentally obtained reflectance spectra.
X-Ray Spectroscopic Investigation of Valence Bands of PdCl2, Pd(ac)2 and Pd(acac)2
Authors: Chikara Sugiura Chikara Sugiura
Published: February 2005

The palladium-Lβ2,15 emission and chlorine-Kβ emission spectra in fluorescence from PdCl2, Pd(OCOCH3)2 (=Pd(ac)2) and Pd(CH3COCHCOCH3)2 (=Pd(acac)2) are measured using a high-resolution two-crystal spectrometer. The Pd Lβ2,15 emission and Cl Kβ emission spectra are presented along with the Pd L
III absorption and Cl K absorption spectra of these compounds reported previously. The measured Pd Lβ2,15 emission spectra consist of a prominent peak with a high-energy structure and are quite alike, in contrast to the case of the Pd L
III absorption spectra. The emission and absorption spectra of PdCl2 are compared with those of K2PdCl4 reported previously and interpreted in terms of the D
2h molecular orbital states of the d
8 metal ion for PdCl2 by Tanino and Kobayashi.
A Model of Thermal Transfer in Czochralski Silicon Molten
Authors: Yamashita Kenichi , Kitagawa Kunihiko , Aoki Toshihiko , Kajita Eiji , Shiraiwa Nobukatsu Fujino
Published: February 2005

Simultaneous multipoint measurement has been performed to determine the temperature of silicon molten of a Czochralski (CZ) system during the growth of a monocrystalline ingot. A high magnitude of temperature fluctuation was found to be totally random without correlation among temperatures of various points in the molten, a phenomenon which could not be explained by models based on a lamina flow. The magnituge of the fluctuation, however, was observed to be related with effective thermal transfer of the molten. A model which took account of thermal transfer induced by local dynamical random motion, a kind of turbulence, of the molten was proposed. The time-averaged temperature distribution taken from the solution of a static diffusion equation with the effective thermal diffusivity agreed very well with the experimental results.
Initial Growth Mechanism for GaAs and GaP on Si Substrate by Metalorganic Chemical Vapor Deposition
Authors: Soga Tetsuo , George Thomas , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: February 2005

The initial stage of epitaxial growth of GaAs and GaP on Si substrates by atmospheric-pressure metalorganic chemical vapor deposition was investigated. GaP tends to grow three-dimensionally and the GaP island is faceted by a (111)-type plane. The island density of GaP increases with increasing V/III ratio and the growth mode changes from three-dimensional to two-dimensional. On the other hand, the island density does not depend on the V/III ratio in the case of GaAs on Si. The island formation mechanisms based on the experimental results are described.
Step-Promoted Surface Reconstruction on Ga-Deposited (100) GaAs During Molecular Beam Epitaxy with Alternating Supply of Ga and As
Authors: Kanamoto Kyozo , Yasunori Tokuda Yasunori Tokuda , Noriaki Tsukada Noriaki Tsukada
Published: February 2005

We have investigated the change in the reflection high-energy electron diffraction pattern during molecular beam epitaxy of GaAs with an alternating supply of gallium and arsenic beams. The surface reconstruction observed during Ga deposition, a (4×8) structure, is found to be affected by the substrate temperature and the surface misorientation from the (100) plane. We show that this reconstruction can preferentially be promoted by regularly arrayed steps having a periodicity comparable to the size of the reconstruction unit cell.
Structure and Electronic Transport of Highly Conductive Langmuir-Blodgett Films of Tridecylmethylammonium-Au(dmit)2
Authors: Miura Yasuhiro F. , Takenaga Mitsuru , Kasai Akinari , Nakamura Takayoshi , Matsumoto Mutsuyoshi , Kawabata Yasujiro
Published: February 2005

Electronic transport measurements are reported for Langmuir-Blodgett (LB) films of tridecylmethylammonium-Au(dmit)2 for 300-4 K. The conductivity after electrochemical oxidation is 30-50 S/cm at room temperature, increases with decreasing temperature, and begins decrease at about 200 K. The conductivity at lower temperatures is explained by two-dimensional variable range hopping (2D VRH). The thermoelectric power (S) is positive and well fitted by a linear combination of the temperature dependence of 2D VRH (S
v\proptT
1/3) and that of metal (S
m\proptT). These results can be explained by a model in which highly conductive metallic regions are separated by thin weakly conductive regions. The UV/visible absorption spectra and the X-ray diffraction patterns indicate that a large structural change occurs accompanied by electrochemical oxidation.
Range of Application for Asymmetric Double Probes
Authors: Fuchs Hiroshi Amemiya
Published: February 2005

Current-voltage characteristics of asymmetric double probes have been measured in hydrogen plasmas. It has been found that up to a critical ratio of the areas, a part of the probe characteristic in the neighborhood of zero voltage is symmetric with respect to a symmetric point. Above that critical ratio, the characteristic approaches that of a single probe. The true single probe characteristic can be obtained only if the area ratio is much larger than the above critical value.
Electrical Methods for Characterizing Directly Bonded Silicon/Silicon Interfaces
Authors: Stefan Bengtsson Stefan Bengtsson , Olof Engström Olof Engström
Published: February 2005

Measurement methods for characterizing the electrical properties of directly bonded Si/Si n-type/n-type or p-type/p-type interfaces are presented. The density of interface states in the bandgap of the semiconductor and the density of interface charge at the bonded interface are determined from measurements of current and capacitance vs applied voltage. The density of interface charge is thus obtained from two different measurements. The two measurement methods are compared and the limitations of the methods are discussed. Also, a high density of interface states at the bonded interface gives rise to a current transient when a voltage step is applied. This can be used as a qualitative estimate of the interface properties.
Structure and Properties of Silicon Titanium Oxide Films Prepared by Plasma-Enhanced Chemical Vapor Deposition Method
Authors: Kamada Takeshi , Kitagawa Masatoshi , Munehiro Shibuya Munehiro Shibuya , Takashi Hirao Takashi Hirao
Published: February 2005

We have developed a novel material of silicon titanium oxide with high dielectric constant and low leakage current. The silicon titanium oxide films were prepared by plasma-enhanced chemical vapor deposition (plasma CVD) with the gas mixture of TiCl4-SiH4-N2O. It was found that these films have intermediate properties of silicon dioxide and titanium dioxide by varying the ratio of SiH4/(SiH4+TiCl4). The properties of silicon titanium oxide nearly corresponded to those of Ta2O5 when the gas mixture ratio was 0.075, with a dielectric constant of 18 and a leakage current density of 2.5×10-8 A/cm2 at 1 MV/cm.
Injection Level Spectroscopy: A Novel Non-Contact Contamination Analysis Technique in Silicon
Authors: Ferenczi George , Tibor Pavelka Tibor Pavelka , Péter Tüttô Péter Tüttô
Published: February 2005

Microwave photoconductivity decay was measured in the function of the excitation light intensity. Using a new approach to analyze recombination lifetime data an experimental method is presented which is capable of producing qualitative lateral distribution maps of different metal contaminants in a silicon wafer.
Analysis of p+-n Junction Capacitance with Three-Dimensional Impurity Profiling Method Using Scanning Tunneling Microscopy
Authors: Tanimoto Masafumi , Takakuni Douseki Takakuni Douseki , Takako Takigami Takako Takigami
Published: February 2005

The p+-n junction capacitance characteristics have been analyzed by a novel three-dimensional impurity profiling method using chemical etching and scanning tunneling microscopy. The calculated capacitance-voltage characteristics for plane and side-wall capacitances agree better with the measured characteristics than does the case with conventional SIMS analysis. It is found that the C-V characteristics for side-wall capacitance scarcely depend on the impurity profile. Moreover, the obtained side-wall capacitance value enables a more accurate simulation of circuit performance. These results show that the proposed STM profiling method is a promising tool for the characterization of submicrometer devices.
Sputtering of Aluminum Film Using Microwave Plasma with High Magnetic Field
Authors: Takehiro Shinobu , Yamanaka Norimasa , Shindo Haruo , Shoso Shingubara Shoso Shingubara , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

A newly developed microwave plasma with magnetic field (2B mode) two times higher than the ECR (electron cyclotron resonance) condition was, for the first time, applied to the sputtering of aluminum film at Ar pressure lower than 5×10-4 Torr. The highly (111)-oriented polycrystal grain structure with no other crystal orientation was obtained by cooling the substrate to -120°C. The degree of (111) orientation was further enhanced by applying negative bias on the substrate. On the other hand, the filling of a half-micron trench of aspect ratio 3 was satisfactorily achieved at 300°C, which was much lower than that by the conventional method employing DC (direct current) magnetron sputtering. The salient feature of 2B mode plasma is the high ionization rate of atoms, more than 50%. Hence, it is most likely that the enhancement of surface diffusion due to the ion bombardment effect on near surface atoms plays the essential role in the lowering of the filling temperature and the enhancement of (111) orientation.
Hot-Wall Chemical-Vapor-Deposition of Amorphous-Silicon and Its Application to Thin-Film Transistors
Authors: Ahn Byung-Chul , Shimizu Kazuhiro , Satoh Tsutomu , Kanoh Hiroshi , Osamu Sugiura Osamu Sugiura , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

Hot-wall chemical vapor deposition of amorphous-silicon has been investigated, aiming at a batch process for thin-film transistors (TFTs). High-performance TFTs (mobility=1.7 cm2/Vs, threshold voltage =9 V and subthreshold voltage swing =0.8 V/decade) have been successfully fabricated. Similar good TFT characteristics were obtained over a wide range of a-Si deposition conditions.
A New Method to Estimate Grain Boundary Trap State Density in Poly-Si TFTs
Authors: Kato Noriji , Yamada So , Nishihara Yoshio , Mario Fuse Mario Fuse , Toshihisa Hamano Toshihisa Hamano
Published: February 2005

A new method of estimating grain boundary trap state density in poly-Si thin film transistors (TFTs) is proposed by modifying an assumption used in Levinson's method. Our method assumes that only the carrier near the surface contributes to the total current, and the other carrier is neglected. Then the carrier density at the surface is used to express the potential barrier height induced at the grain boundary instead of the averaged carrier density as in Levinson's method. The validity of our assumption is investigated using our two-dimensional device simulator, and it is shown that our assumption on the carrier density is suitable to derive the true trap state density.
Control of GaAs and InGaAs Insulator-Semiconductor and Metal-Semiconductor Interfaces by Ultrathin Molecular Beam Epitaxy Si Layers
Authors: Akazawa Masamichi , Hirotatsu Ishii Hirotatsu Ishii , Hideki Hasegawa Hideki Hasegawa
Published: February 2005

Removal or control of Fermi level pinning is attempted using an ultrathin molecular beam epitaxy (MBE) Si interface control layer (Si ICL) for insulator-semiconductor (I-S) and metal-semiconductor (M-S) interfaces of GaAs and InGaAs. For successful removal of Fermi level pinning at the I-S interface, the Si ICL should maintain an ordered pseudomorphic structure. The optimum thickness of the Si ICL is about 10 Å. Formation of such a Si ICL alone does not remove pinning; subsequent deposition of a SiO2 film is necessary for unpinning. Pinning at the air-exposed surfaces can be removed by combining an HF surface treatment with the Si ICL technique. The Si ICL technique is promising for controlling barrier heights at M-S interfaces.
In Situ Surface State Spectroscopy by Photoluminescence and Surface Current Transport for Compound Semiconductors
Authors: Saitoh Toshiya , Hirotake Iwadate Hirotake Iwadate , Hideki Hasegawa Hideki Hasegawa
Published: February 2005

By a rigorous computer analysis of the surface recombination process, it is shown that the surface state distributions on semiconductor free surfaces can be determined from a measurement of the dependence of band-edge photoluminescence intensity on the excitation intensity. The measurement of the Fermi level pinning position in the dark by the surface current transport measurement avoids the possible ambiguity of the interpretation. The new technique is successfully applied to variously treated GaAs surfaces and to passivated InGaAs surfaces with and without the ultrathin Si interface control layer.
In SituCharacterization of the Initial Growth Stage of GaAs on Si by Coaxial Impact-Collision Ion Scattering Spectroscopy
Authors: Hashimoto Akihiro , Sugiyama Naoharu , Masao Tamura Masao Tamura
Published: February 2005

The initial growth stage of GaAs on Si has been characterized in situ by coaxial impact-collision ion scattering spectroscopy (CAICISS). The behavior of As atoms on the Si surface and at the step sites is analyzed. The results of analysis on the initial growth stage strongly suggest that the three-dimensional island growth of GaAs on Si occurs even in 1-monolayer (ML) GaAs growth.
Lateral Metalorganic Molecular Beam Epitaxy of GaAs on Patterned (1̄1̄1̄)B Substrates
Authors: Nomura Yasuhiko , Morishita Yoshitaka , Goto Sigeo , Isu Yoshifumi Katayama
Published: February 2005

GaAs layers were grown on patterned (1̄1̄1̄)B substrates having (1̄2̄2̄)A sidewalls with various arsenic fluxes at a fixed temperature of 480°C by metalorganic molecular beam epitaxy (MOMBE) using trimethylgallium (TMGa) and metal arsenic. Vertical growth rate on the top and bottom (1̄1̄1̄)B surfaces decreased rapidly as the arsenic flux was increased. For arsenic fluxes of 2.0×10-3 Pa and more, only lateral epitaxy on the (1̄2̄2̄)A sidewall was achieved. Real-time scanning microprobe reflection high-energy electron diffraction (µ-RHEED) observations showed that the surface smoothness of the epitaxial layer was maintained throughout the growth time under the optimized condition.
Low-Temperature Substrate Annealing of Vicinal Si(100) for Epitaxial Growth of GaAs on Si
Authors: Okada Yoshitaka , Shimomura Hirofumi , Takeyoshi Sugaya Takeyoshi Sugaya , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Effects of atomic hydrogen irradiation on vicinal Si(100) surfaces have been investigated by reflection high-energy electron diffraction (RHEED) and scanning tunneling microscope (STM) observations. Interplay of the two different Si hydride phases and dynamic changes in the surface reconstruction have been observed and studied in detail. It has also been shown that removal of oxide from Si surface and a single-domain (2×1) Si surface can be obtained at annealing temperatures below 750°C with atomic hydrogen irradiation, much lower than those usually requied for the conventional thermal treatment methods.
Effect of Annealing and Sulfur Passivation of GaAs Surface in ZnSe/GaAs Heterostructure
Authors: Murawala Prakash A. , Tsuji Osamu , Fujita Shizuo , Fujita Shigeo
Published: February 2005

We report the effect of annealing and sulfur (S) passivation of GaAs surface on the interface characteristics and interdiffusion problem in ZnSe/GaAs heterostructures whose ZnSe layers are grown by atomic layer epitaxy (ALE) and metalorganic molecular beam epitaxy (MOMBE). The photoluminescence (PL) intensity of self-activated centers created due to interdiffusion at 500°C in the conventionally grown sample is 3-14 times higher than that in the S-passivated sample. Secondary ion mass spectroscopy (SIMS) data suggest that after annealing, Ga and As concentration in the ZnSe epilayer is lower in S-passivated materials. These features suggest that heterostructures are thermally stable in S-passivated material. As a result of S-passivation, full width at half maximum (FWHM) values of X-ray rocking curves are greatly reduced and we could, without postgrowth annealing, achieve well-defined C-V characteristics of a metal/pseudoinsulating ZnSe/GaAs metal-insulator-semiconductor (MIS) diode. Sulfur passivation is an important tool for the fabrication of high-quality heterostructures of II-VI and III-V semiconductors.
Bi12SiO20 Thin Films Grown by Electron Cyclotron Resonance Plasma Sputtering with a Bi and Si Multitarget System
Authors: Koji Nomura Koji Nomura , Hisahito Ogawa Hisahito Ogawa
Published: February 2005

Bi12SiO20 thin films have been prepared on glass and (0001) sapphire substrates by ECR plasma sputtering with a Bi and Si multitarget system. Polycrystalline thin films of δ-phase Bi12SiO20 have been obtained without any substrate heating. These films can be transformed into γ-phase Bi12SiO20 by heat treatment above 400°C in air and show a large photoconductivity in the range of 380-460 nm. Epitaxial thin films of γ-phase Bi12SiO20 have been obtained on (0001) sapphire substrates at the substrate temperature of 600°C during the sputtering process. Excellent quadratic electrooptic effects for these epitaxial thin films are successfully observed for the first time, and a spatial light modulator using this γ-phase Bi12SiO20 thin film has also been demonstrated. The details of the preparation, structure and some electrical and electrooptic properties of the Bi12SiO20 thin films are described.
Characterization of Novel Cu-Al-Se Films Grown by Molecular Beam Epitaxy
Authors: Yoshio Morita Yoshio Morita , Tadashi Narusawa Tadashi Narusawa
Published: February 2005

Undoped and Zn-doped Cu-Al-Se films have been grown on GaAs(100) substrates by molecular beam epitaxy, and their optical and electrical properties have been characterized. The compositions of grown films are about 50 at%Cu, 10 at%Al and 40 at%Se, and single-crystal films are obtained. The photoluminescence spectrum of an undoped film exhibits a blue emission at 77 K and room temperature. The undoped film annealed at 550°C for 16 h shows p-type conductivity with the resistivity of 6.9×10-3 Ω·cm, the carrier concentration of 2.5×1018 cm-3 and the mobility of 370 cm2·V-1·s-1. Zn-doped as-grown film shows n-type conductivity. These characteristics suggest the possibility of p-n junction optical devices fabricated with the novel Cu-Al-Se films. On the other hand, the current-voltage characteristic of Cl-doped ZnSe/undoped Cu-Al-Se/ p-GaAs exhibits a rectifying characteristic with the turn-on voltage of 2.7 V.
Preparation and Properties of Ultrathin High-Tc Superconducting Films on Si
Authors: Myoren Hiroaki , Harada Kanji , Miyamoto Aiko , Naokazu Miyamoto Naokazu Miyamoto , Yukio Osaka Yukio Osaka
Published: February 2005

Ultrathin Ba2YCu3O
x
films with thickness down to 7 nm were grown epitaxially on a Si(100) substrate using buffer layers (Y2O3(10 nm) and YSZ(40 nm)). These films show metallic behavior and full superconductivity through revealing broadened transitions. The critical current densities at 40 K are about 5×106 A/cm2 and 5×105 A/cm2 for 100 nm- and 28 nm-thick films, respectively.
Layer-by-Layer Growth of Bi-Sr-Ca-Cu-O Superconducting Films by Molecular Beam Epitaxy
Authors: Ishibashi Takayuki , Okada Yoshitaka , Yokoyama Shin , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Layer-by-layer growth of Bi2Sr2Ca
n-1Cu
n
O
x
oxide superconducting films by molecular beam epitaxy (MBE) have been confirmed by observation of intensity oscillations in the reflection high-energy electron diffraction (RHEED) patterns. The period of one oscillation corresponded to a growth time of a half unit cell. The films have been prepared by a coevaporation technique, In which the Bi, Sr, Ca and Cu metal sources were evaporated simultaneously with Knudsen cells under an oxygen/ozone mixture (ozone content of 10%) atmosphere. The 2212 phases fabricated exhibited critical temperatures below 70 K.
Superconductivity in BiSrCaCuO Superlattices: Two-Dimensional Properties of CuO Planes
Authors: Nakao Masao , Furukawa Hiroaki , Ryohkan Yuasa Ryohkan Yuasa , Shuji Fujiwara Shuji Fujiwara
Published: February 2005

We report resistive measurements on epitaxial superlattices consisting of alternating Bi2Sr2CaCu2O8 (2212) and Bi2Sr2CuO6 (2201) layers grown by atomic-layer-by-layer molecular beam epitaxy (MBE) using oxygen radical beams. The influence of interplane coupling between Cu-O planes was studied by varying the superlattice sequence of different c-axis half-unit cells. A single-half-unit-cell-thick 2212 layer was found to be superconducting in a 2201 matrix, independent of the conductivity and the thickness of neighboring 2201 layers. The fact that all of our superlattices showed superconductivity essentially equal to that of a 2212 single-phase film suggests that this cuprate is a two-dimensional superconductor due to its Cu-O double planes.
A Side-Entry Helium-Cooled Stage for Electron Microscopy
Authors: Seiichi Murooka Seiichi Murooka , Hideo Fujiki Hideo Fujiki
Published: February 2005

A liquid-helium-cooled specimen stage for an electron microscope has been designed and built. It attaches to the microscope's side-entry goniometer and contains a small continuous flow cryostat. No modifications are required for the microscope, and installation is easily accomplished. Using this stage, specimen temperatures below 7.0 K were obtained.
Effect of Annealing Conditions on the Tc of the Y2Ba4Cu7O15-x Superconductor
Authors: Murakami Hirohiko , Yaegahi Seiji , Yuh Shiohara Yuh Shiohara , Shoji Tanaka Shoji Tanaka
Published: February 2005

The superconductor Y2Ba4Cu7O15-x
was prepared in bulk form, and the effect of annealing conditions on superconductivity was investigated by annealing under various conditions. Single-phase 247 samples were prepared at 870°C in 1 atm oxygen. The T
c was found to decrease from a maximum of 82 K for a sample quenched from 300°C to a minimum of 40 K for a sample quenched from 870°C.
Magnetic Properties of Sodium-Modified Iron-Oxide Powders Synthesized by Sol-Gel Method
Authors: Yamanobe Yasunori , Yamaguchi Kazuhiro , Koji Matsumoto Koji Matsumoto , Toshitaka Fujii Toshitaka Fujii
Published: February 2005

Spinel-type ferrites of the sodium-modified iron-oxide (Na-Fe-O) system were synthesized by using a sol-gel method. The maximum magnetic moment of 50 emu/g was obtained at the sodium concentration of C
Na=0.1 to 0.2 (the mol ration of sodium to the sum of sodium and iron), which is about 1.5 times larger than that of non-substituted ones. Monotropic phase transition temperature from the γ-Fe2O3 phase to the α-Fe2O3 phase was shifted to higher temperature by substituting a small amount of sodium and the highest transition temperature reaches as high as about 600°C for C
Na=0.2, where the crystal structure of spinel was maintained except elongation of the lattice parameter, which results in the decreases of Curie temperature and magnetic hyperfine field. Improvement in thermal stability of γ-Fe2O3 is considered to be due to the formation of sodium-modified γ-Fe2O3.
Measurement of High-Temperature Absorption Spectra on Heavily Doped KCl:Pb2+ Crystal
Authors: Hiroshi Asada Hiroshi Asada
Published: February 2005

Optical spectra of KCl crystals heavily doped with Pb2+ ions are investigated at temperatures between liquid nitrogen temperature (LNT) and 600°C. Aggregates and precipitates are found in heavily doped samples. With the rise of temperature, the aggregates are decomposed at temperatures near 425°C and the precipitates are formed near 400°C. The aggregates are different in type from the ones observed hitherto. The formation of the precipitates with the rise of temperature is observed. It is shown by this experiment that high-temperature absorption measurement is a powerful method for investigating the behavior of the heavily doped impurity.
Dipolar Effect in Thermal-Pulse-Current Responses of Polar Polymers
Authors: Suzuoki Yasuo , Kaneko Kazue , Yokota Yasushi , Teruyoshi Mizutani Teruyoshi Mizutani , Masayuki Ieda Masayuki Ieda
Published: February 2005

Thermal-pulse-current (TPC) measurement, which is one of the powerful techniques for direct probing of space charge in dielectrics, was carried out on polyvinylidene fluoride (PVDF) films. The rise time of the observed TPC responses was long. The TPC responses in both anode and cathode illuminations were symmetric with opposite polarities and the intensity was linear with the field under low fields. These and the results of computer simulation suggested that the TPC responses reflected the dipolar polarization. The relaxation time of dipolar polarization estimated from the TPC rise time was of the same order of magnitude as that of the α-crystalline parts (∼10-3 s).
Hardness of Quasicrystals
Authors: Takeuchi Shin , Iwanaga Hiroshi , Shibuya Tadaharu
Published: February 2005

Vickers hardness measurements have been made at room temperature for four thermodynamically stable quasicrystals. The hardness value of Al-Li-Cu icosahedral quasicrystal is about 500 (kg/mm2) and those of Al-transition metal quasicrystals are commonly around 1000, which is extremely high for aluminum based alloys. Anisotropy in the hardness in Al-Co-Ni decagonal quasicrystal is rather small.
Observation of Ramsey-Type Resonant Fringe Using a Cylindrical Microwave Cavity for a Diode Laser-Pumped Rb Beam Atomic Clock
Authors: Furuta Hiroyuki , Hiromasa Suzuki Hiromasa Suzuki , Motoichi Ohtsu Motoichi Ohtsu
Published: February 2005

A novel Ramsey-type resonance signal is observed by using a simple microwave cylindrical cavity in a diode laser-pumped rubidium atomic clock. Its linewidth is 1.1 kHz. The signal lineshapes depend on the modal profile of the microwave magnetic field inside the cavity. The lineshapes are reproduced by numerical calculation. Conditions to achieve the maximum frequency discrimination sensitivity are derived by the theoretical analysis.
Photoluminescence and Acceptor State of Na in ZnSe
Authors: Isshiki Minoru , Itoga Toshihiko , Masumoto Katashi , Uchida Katsumi Mochizuki
Published: February 2005

Sodium was incorporated into high-purity ZnSe single crystals by dipping the crystal into molten Se-base Na alloys. The I
1
Na line and two types of donor-acceptor pair (DAP) emissions were observed. An acceptor binding energy of 117 meV was obtained for Na by analyzing the selective photoluminescence spectra on the I
1
Na line and the excitation intensity dependence of the peak energy of DAP emissions. It is confirmed that the P emission observed in DAP emission is due to the recombination between the Na acceptor and Ga donor.
Properties of Sawtooth-Doping Superlattice with Different Delta-Doping Densities
Authors: Wen-Chau Liu Wen-Chau Liu , Chung-Yih Sun Chung-Yih Sun
Published: February 2005

The electronic transport properties in a sawtooth-doping superlattice (SDS) with different delta-doping densities have been studied. Multiple-state negative differential resistance (NDR) performance is exhibited due to the strong field effect and the avalanche multiplication mechanism. The different delta-doping densities contribute to the different barrier heights in the superlattice periods which cause various influences on the whole transport properties. Therefore, the different NDR phenomena in the current-voltage characteristics are clearly observed.
Simultaneous Fabrication of Vertical and 45° Mirrors of InP for Surface-Emitting Lasers Using Inclined Cl Ion Beams
Authors: Mutoh Katsuhiko , Wakabayashi Shin-ichi , Toyoda Yukio , Masato Nakajima Masato Nakajima
Published: February 2005

Reactive ion beam etching (RIBE) of InP using inclined Cl ion beams has been studied. Straight-sloping side walls of InP grooves are fabricated using those of SiO2 as etching masks. By controlling the wall inclination of the SiO2 mask and the etch rate ratio of InP to SiO2, an InP groove with side-wall inclinations of 90° and 45° is obtained using one RIBE process. Furthermore, the walls of the groove are used for fabrication of the InGaAsP/InP surface-emitting laser with a Fabry-Perot resonator and a 45° mirror. A threshold current of 40 mA is obtained for the laser under continuous-wave operation at room temperature.
Coherent Tunneling and Voltage Amplification
Authors: Moichiro Nagae Moichiro Nagae
Published: February 2005

We analyze the flow of electrons injected continuously into one metal side of a specially biased metal-insulator-metal tunnel junction, where this metal part has a sufficiently long mean free path. These injected electrons are energetic and yield an electric double layer at the end of this metal region on the insulator side. Then, an appreciable amount of voltage difference (some type of emf) appears across both ends of this metal layer. From results of calculations, we discuss the possibility of such a phenomenon.
Electromigration Effect on Low Frequency Noise in Al Thin Films
Authors: Liou D. M. , J. Gong J. Gong , C. C. Chen C. C. Chen
Published: February 2005

The change in the noise spectrum was used to characterize the electromigration damage of aluminum thin-film resistors. The 1/f2 noise spectrum was observed in the artificially stressed samples when the measurement current was flowing in the same direction as the stress current. However, when the same amount of measurement current flowed into the same sample from the other end, the sample showed a 1/f noise spectrum. The scanning electron microscope was used to analyze the damaged portion of the sample.
Dielectric Properties of Two Polar Nematic Liquid Crystals
Authors: Belarbi-Massouras Z. , Guillaud G. , Tournilhac F. , Acourag H. , Khelifa B.
Published: February 2005

We report in this paper the dielectric properties of two polar nematic liquid crystals p-methoxybenzylidene-p'cyanoaniline (MBCA) and p-cyanobenzylidene-p'methoxyaniline (CBMA). The effect induced by dc and ac electric fields as well as magnetic field resulting to a deformation of the nematic director was studied at 10 kHz and 1 kHz. The dielectric anisotropies, splay elastic constants and diamagnetic anisotropies as well as the correlation factors are investigated by capacitance measurements. These results are discussed in terms of molecular properties and molecular degree association.
Preparation of Ferroelectric PbTiO3 Thin Film by Reactive Sputtering
Authors: Okamura Takeshi , Adachi Masatoshi , Tadashi Shiosaki Tadashi Shiosaki , Akira Kawabata Akira Kawabata
Published: February 2005

Ferroelectric PbTiO3 thin films have been successfully obtained. The films were fabricated by reactive sputtering using a simple metal composite as a target. Without postannealing, the films with perovskite structure have been obtained at substrate temperatures of 600-620°C. The spontaneous polarization (P
s) and the coercive field (E
c) of a 0.70 µm-thick film were measured as 37 µC/cm2 and 86 kV/cm, respectively.
Self-Recovery from Alignment Damage under AC Fields in Antiferroelectric and Ferroelectric Liquid Crystal Cells
Authors: Itoh Keizou , Johno Masahiro , Takanishi Yoichi , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

Alignment recovery from damage has been confirmed to occur under an AC electric field, e.g., 30 Vpp·µm-1, in antiferroelectric chiral smectic liquid crystal cells of MHPOBC and a related fluorinated compound. The recovery partly results from internal shearing produced by reversible layer switching between bookshelf and quasi-bookshelf. Contrary to the widely accepted notion, even in a ferroelectric liquid crystal cell of a compound similar to MHPOBC, reversible layer deformation due to an electric field has been observed from X-ray diffraction and a similar alignment recovery from damage has also been confirmed to occur.
Preparation of Pb(Mg1/3Nb2/3)O3-PbTiO3 Powder by a Wet Chemical Process
Authors: Ando Toshinori , Ryuji Suyama Ryuji Suyama , Kei Tanemoto Kei Tanemoto
Published: February 2005

A modified oxalate method in ethanol is applied to preparation of 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 fine powder. Calcination at 800°C and sintering at a low temperature of 900°C are possible for the powder. The precipitation process and the mechanism of calcination are discussed.
Nature of Oxygen Donors and Radiation Defects in Oxygen-Doped Germanium
Authors: Fukuoka Noboru , Atobe Kozo , Matsuda Makoto Honda
Published: February 2005

The nature of oxygen donors and radiation defects in oxygen-doped germanium were studied through measurements of the infrared absorption spectrum, deep level transient spectroscopy spectrum and carrier concentration. It is revealed that a new donor is not formed in oxygen-doped germanium. An A-center (interstitial oxygen-vacancy pair) forms a complex with a thermal donor in its anneallng stage at 60°C-140°C. The introduction rate of defects by 1.5 MeV electron irradiation was enhanced in thermal-donor-doped samples.
Ion Beam Induced Damage in Epitaxial TiN Films
Authors: Padmanabhan Karur R. , Saitoh Kazuo , Yoshiko Miyagawa Yoshiko Miyagawa , Soji Miyagawa Soji Miyagawa
Published: February 2005

Thin epitaxial TiN films have been deposited on MgO(100) substrate by ion plating technique. Both RHEED and XRD analysis indicate crystalline quality of the film. Ion channeling measurements show that the epitaxial TiN films have comparable minimum yield to that of the substrate. The damage produced in the film and the substrate lattice due to ion implantation have been investigated by the measurement of the increase in χ min in the aligned spectrum. The presence of a sharp interface in the RBS and AES spectrum confirmed the absence of any ion induced mixing. The measured minimum yield from RBS-C analysis for 500 keV and 2 MeV Si+, Kr+ and Au+ implanted epitaxial TiN films indicate that the disorder is dependent on damage efficiency which is a function of ion mass and energy.
Simultaneous Observation of Sub- and Above Threshold Electron Irradiation Induced Defects in GaAs
Authors: Auret F. D. , Bredell L. J. , G. Myburg G. Myburg , W. O. Barnard W. O. Barnard
Published: February 2005

Sub- and above threshold defects were introduced in n-type OMVPE grown GaAs during 3 keV and 3 MeV electron irradiation, respectively. The electrical properties of these defects were determined by DLTS measurements in samples that contained subthreshold defects only, above threshold defects only, as well as samples that contained both types of defects. A careful examination of the low temperature DLTS peaks revealed that although the sub- and above threshold defects have similar properties, they are nevertheless distinguishable from each other and are therefore not the same as has previously been speculated.
Some Characteristics of the Zero-Temperature-Coefficient Capacitance of an MOS Capacitor in Accumulation
Authors: C. H. Ling C. H. Ling
Published: February 2005

Theoretical consideration shows that the silicon component of the MOS capacitor exhibits a zero temperature coefficient of capacitance for a silicon surface biased in accumulation. A unique surface potential, which can be expressed in terms of material properties, exists at which the surface capacitance becomes independent of temperature. Capacitance-voltage plots for temperatures within 50°C of room temperature provide experimental evidence in support of the theory. A gate bias V
x corresponding to this unique surface potential has been observed. However, a slight broadening of V
x into a small spot extending some 20 mV generally results, and has been shown to be due to the presence of the gate oxide capacitance. V
x is relatively constant over the range of signal frequencies, 10-100 kHz, but varies substantially at higher frequencies. V
x also shows a linear dependence on the gate oxide thickness decreasing at the rate of ∼1 V/2000 Å.
Preparation and Characterization of Grain Boundary Josephson Junction from Amorphous Thin Film
Authors: Shinohara Toshiyuki , Enami Hiroyoshi , Kawahara Nobuaki , Kawabata Sanemasa , Imura Hiroki Hoshizaki
Published: February 2005

To prepare the grain boundary Josephson junction, Y-Ba-Cu-O amorphous thin film was first etched into a bridge shape and then annealed at a high temperature, 990°C, to form grain boundaries. The bridge thus prepared showed clear Shapiro steps under the irradiation of microwaves at 4.2 K. Grains of the films sensitively varied their structures, sizes and electric properties with annealing temperature. The grains annealed at a lower temperature, 960°C, were as small as a few micrometers or less. Large grains appeared when the annealing temperature became higher, and the higher the annealing temperature, the greater the number of large grains, untill 990°C. The bridge of 5 µm in width that had grains over 10 µm in size exhibited a.c. Josephson effect, but the effect was not observed with the bridge which consisted of only small grains of a few µm.
Growth of Buffer Layers on Si Substrate for High-Tc Superconducting Thin Films
Authors: Harada Keizo , Nakanishi Hidenori , Hideo Itozaki Hideo Itozaki , Shuji Yazu Shuji Yazu
Published: February 2005

We have investigated the crystalline properties and surface morphology of the buffer layers of Y2O3, ZrO2 and Y2O3/ZrO2 on a Si(100) substrate for a superconducting thin film. The results of RHEED and X-ray diffraction indicate the hetero-epitaxial growth of buffer layers on Si(100) substrates. Epitaxial planes of the buffer layers on the Si(100) surface are (110), (100) and (100)/(100) for Y2O3, ZrO2 and Y2O3/ZrO2, respectively. YBa2Cu3O7-x
thin films have been grown on Si with each buffer layer. The highest critical temperature obtained was 88 K on the Si with the Y2O3/ZrO2 buffer layer.
Synthesis and Characterization of Nb/Al2O3 Multilayer Superconductors
Authors: Kamiguchi Yuzo , Ikebe Manabu , Yoshihisa Obi Yoshihisa Obi , Hiroyasu Fujimori Hiroyasu Fujimori
Published: February 2005

The metal/insulator multilayer superconductor, Nb/Al2O3, has been prepared by use of a dual sputtering technique. Sample characterization has been made by X-ray diffraction and electron transport measurements. The superconducting transition temperature T
c and the upper critical fields parallel and perpendicular to the multilayer plane have been examined as a function of Nb and Al2O3 sublayer thickness. Anisotropy of the critical fields is analyzed on the basis of the Josephson tunneling model for a quasi-two-dimensional superconductor and the strength of the interlayer Josephson coupling through the Al2O3 sublayer is evaluated.
35Cl Nuclear Quadrupole Resonance in Some Solid-Mixtures of p-Dichlorobenzene
Authors: Amitha B. , S. K. Roy S. K. Roy , J. Uchil J. Uchil
Published: February 2005

The impurity effects on 35Cl NQR frequency in various binary systems of p-dichlorobenzene as solvent and napthalene derivatives as solute have been studied in the range of solute concentration from 0-50% at room temperature. It is found that there is a critical range of solute concentration where both β and α-phase of p-dichlorobenzene coexist. Below the lower limit of critical concentration the NQR frequency corresponds to β-phase of p-dichlorobenzene. An increase in the solute concentration is found to induce a phase transition and the solid mixture at higher concentration consists of micro crystals belonging to both β and α-phase of p-dichlorobenzene upto the upper limit of critical concentration beyond which only α-phase is found to be present. The phase diagrams indicate that the solubility of the two components in each other is limited. The effect caused by the formation of eutectic mixture hardly disturbs the electric field gradient.
Investigation on the Photocurrent Decay Kinetics in Polyenes
Authors: Pal Prabir , Dilip Ghosh Dilip Ghosh , Tridibendra N. Misra Tridibendra N. Misra
Published: February 2005

The photoconductivity decay in a number of polyene crystals has been studied. Two photocarrier decay mechanisms have been observed. A fast decay has been observed in a short time domain whereas in a longer time domain, a slow decay is manifested. Most of the photocurrent decays in the shorter time domain. The decay in the shorter time domain is dominant shallow trap limited, and the trap depth has been obtained from the activation energy of mean decay time, τ0. Field and temperature dependence studies in the longer time domain reveal the existence of additional traps distributed exponentially in some polyenes.Tc, the exponential trap distribution parameter, changes with applied field, but there is no appreciable change with sample temperature. Field effect onTchas been attributed to the field effect on its trapping rate.
A Method of Polarization Stabilization in Surface Emitting Lasers
Authors: Shimizu Mitsuaki , Mukaihara Toshikazu , Baba Toshihiko , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

In this paper, we propose a surface emitting laser structure for controlling its output polarization. By preparing high refractive index films on the side walls of a dielectric multilayer reflector, we can provide a differential loss to the orthogonal polarizations. We estimate the reflectivity dependence on the polarization direction of this reflector and conclude that the control of polarization direction is possible by employing this structure.
Crystallization and Anomalous Thermal Expansion of Amorphous Ni-P Alloy
Authors: Yamamoto Motokazu , Hiramatsu Koichi Shirai
Published: February 2005

The relation between the crystallization and the specific linear expansion of an amorphous Ni-P alloy caused by heating was investigated. When the amorphous Ni-P was heated from 27°C to 450°C, Ni5P4 crystals containing Ni, NiP crystals containing Ni, and Ni3P and NiP2 crystals containing Ni grew at 270°C, 370°C and 410°C, respectively.
Alternatively, when the amorphous Ni-P was heated under the same conditions as above, anomalous specific linear expansion was observed at the above-mentioned three temperatures. By the use of the results of the existence ratio of crystals and X-ray measurement of their thermal expansion, it was possible to calculate the anomalous specific linear expansion as a function of temperature.