bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Quality YBa2Cu3O7-δ Thin Films Grown on SrLaAlO4(001) and (1118) Substrates
Authors: Chai Kwo-Hsiung Young
Published: February 2005

SrLaAlO4 (SLAO) was used as a substrate for the epitaxial growth of YBa2Cu3O7-δ (YBCO) thin films. This material has dielectric properties comparable to those of the commonly used LaAlO3 substrate. The lattice mismatch between SLAO (001) and YBCO (001) is about 3%. Two substrate orientations, cleaved (001) and polished (1118), have been used in this study. YBCO thin films were grown epitaxially from both orientations by in situ laser ablation. The stepped morphology of the cleaved SLAO (001) surface promoted the growth of YBCO along the a-axis. In the case of the SLAO (1118), YBCO (1118) was grown with its c-axis aligned along the c-axis of SLAO. The YBCO (1118) has a T
c of over 90 K with a transition width of 0.5 K, which indicates a high-quality superconductor.
Effects of Anthracene Doping on Electrical and Light-Emitting Behavior of 8-Hydroxyquinoline-Aluminum-Based Electroluminescent Devices
Authors: Takeuchi Manabu , Masui Hisashi , Kikuma Isao , Masui Masayoshi , Tetsuo Muranoi Tetsuo Muranoi , Tatsuaki Wada Tatsuaki Wada
Published: February 2005

Organic electroluminescent (EL) cells consisting of an anthracene-doped 8-hydroxyquinoline aluminum light-emitting layer and a hole transport layer were prepared by co-evaporation, and their electrical and light-emitting behavior was examined. It was confirmed that anthracene doping increased the available current density of the EL cells and EL efficiency, which caused an increase in EL brightness. However, the EL spectrum was only slightly affected by the anthracene doping.
Epitaxial SrTiO3 Thin Films Grown by ArF Excimer Laser Deposition
Authors: Hirano Takashi , Fujii Tatsuhiko , Fujino Kozo , Ken Sakuta Ken Sakuta , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

SrTiO3 (STO) thin films were prepared by an ArF excimer laser deposition method. At the growth temperature of 630°C, the natural orientation of STO was significantly changed from (111) to (100) and (110). The ratio of X-ray diffraction intensities (100)/(200) was closest to the ideal value when grown at 660°C, resulting in minimized disorder of atomic arrangement. Epitaxial STO films were obtained on STO(100) and MgO(100) substrates, and on an YBaCuO(001) epitaxial film. They showed resistivity in excess of 5×1010 Ω·cm and dielectric constant as high as 140ε0 at room temperature. The maximum dielectric constant of 440ε0 was obtained at 40 K.
Ion Incident Angle Dependence of Ridge Shapes Formed on [111] Oriented Gd3Ga5O12 by Ion Beam Etching
Authors: Katoh Yujiro , Sugimoto Naoto , Akiyuki Tate Akiyuki Tate , Atsushi Shibukawa Atsushi Shibukawa
Published: February 2005

A ridge pattern is formed on a [111] oriented Gd3Ga5O12 (GGG) substrate using an argon ion-beam etching at various ion incident angles between 90° and 45°. The relation between the ridge shapes and the ion incident angles is studied. The applicability of a phosphoric acid treatment after the ion-beam etching to smooth the ridge side wall is also examined. The ridge shape strongly depends on the ion incident angle. The phosphoric acid treatment causes a noticeable change of ridge shape dependent on the GGG crystal structure.
Photoinduced Displacement Current in Polyimide Langmuir-Blodgett Films Deposited on Au Electrodes
Authors: Atsushi Fukuda Atsushi Fukuda , Mitsumasa Iwamoto Mitsumasa Iwamoto
Published: February 2005

The photoinduced displacement current across polyimide (PI) Langmuir-Blodgett (LB) films incorporated in Au/PI/air-gap/Au structures was investigated without the application of an external electric field. Transient displacement current was found to be produced by photoirradiation with a wavelength of 400 nm, because carriers were generated in PI LB films and were then conveyed along the electric field established in a Schottky depletion region in the PI LB films.
Polyamic Acid Langmuir-Blodgett Film for Liquid Crystal Alignment
Authors: Sasaki Takashi , Nishikawa Hiroyuki Fujii
Published: February 2005

A method to prepare polyamic acid Langmuir-Blodgett (LB) film has been established for a nematic liquid crystal alignment layer. It consists of two steps: (1) LB deposition of polyamic acid alkylamine salt, and (2) conversion of the LB film obtained to polyamic acid LB film by removing the alkylamine by immersion in acetic anhydride. The present LB film shows an excellent ability for nematic liquid crystal alignment without the conventional rubbing process.
Smooth and Vertical InP Reactive Ion Beam Etching with Cl2 ECR Plasma
Authors: Yoshikawa Takashi , Kohmoto Shigeru , Ozaki Masami , Hamao Noboru , Sugimoto Yoshimasa , Sugimoto Mitsunori , Asakawa Kiyoshi
Published: February 2005

Smooth and vertical InP reactive ion beam etching has been achieved with electron cyclotron resonance Cl2 plasma at high ion energy (≥900 eV), high temperature (230°C) and relatively low Cl2 pressure (∼10-4 Torr). Smooth etching of an InP system by Cl2 plasma has often been reported as difficult compared to that of the GaAs system due to low volatility of reactive products such as InCl
x
. In the present work, precise control of incident ion energy and Cl2 pressure contributed to the improvement of both the vertical profile and bottom smooth surface under high substrate temperature (∼200°C). Vertical profiles were easily achieved even at high temperatures by varying the Cl2 pressure. While etching conditions suitable for vertical wall-formation were maintained, surface morphology was drastically improved by increasing ion energy above 900 eV and the bottom roughness became less than 100 nm at 1450 eV.
Pressure-Induced Paschen-Back Effect of R-Lines in Alexandrite under High Magnetic Field
Authors: Kuroda Noritaka , Kanda Hiroyuki , Kido Giyuu , Takeda Masayasu , Yuichiro Nishina Yuichiro Nishina , Yasuaki Nakagawa Yasuaki Nakagawa
Published: February 2005

Magneto-luminescence of R-lines has been studied in alexandrite subjected to quasi-hydrostatic pressures near 8 GPa at 77 K. In contrast to the previous experiment under lower pressures, the Zeeman spectrum exhibits Paschen-Back behavior if a magnetic field up to 15 T is applied parallel to the b- and c-axes of the crystal. This phenomenon reflects that the transverse moment of spins of the 2E term of Cr3+ ions is significantly reduced by pressure. Pressure strengthens the Ising character of the spins by elevating axial symmetry of the crystal field.
Selective Growth of Polyacetylene Narrow Wires Utilizing Capillary Action of Catalyst Solution in Grooves
Authors: Sasaki Nobuo , Yoshihiro Takao Yoshihiro Takao , Nagisa Ohsako Nagisa Ohsako
Published: February 2005

Polyacetylene narrow wires were selectively grown in SiO2 grooves. A substrate with grooves was held upright and the lower edge was dipped in a pool of the catalyst solution. The solution rised up in the groove by capillary action. A polyacetylene wire 0.1 µm wide, 0.2 µm thick, and 8 mm long was synthesized in a groove 0.2 µm wide and 0.55 µm deep. This length of the wire was limited by that of the grooves. Theoretical calculation shows that the catalyst solution can reach a height of 26 m in this case. Electrical conductivity was 300 S/cm for heavily iodine-doped wires formed in grooves 0.5 µm wide and 0.55 µm deep.
Stable Operation of AlGaAs/GaAs Light-Emitting Diodes Fabricated on Si Substrate
Authors: Wada Naoki , Yoshimi Shinichi , Sakai Shiro , Chun Lin Shao Chun Lin Shao , Masuo Fukui Masuo Fukui
Published: February 2005

An AlGaAs/GaAs LED (light-emitting diode) with very small degradation is fabricated in an UCGAS (undercut GaAs on Si) structure for the first time. The 43 K photoluminescence data show that the stress in UCGAS annealed at 400°C is reduced to less than 1×108 dyn/cm2. The output power from the UCGAS LED under a constant current of 800 A/cm2 degrades to 94% of the original value in the first several hours and subsequently maintains constant output for more than 1000 hours. On the other hand, the output power emitted from the conventional mesa-type LED which contains residual stress of more than 109 dyn/cm2 degrades quickly.
Preparation of YBa2Cu3Ox Thin Films by Layer-by-Layer Metalorganic Chemical Vapor Deposition
Authors: Fujii Kouji , Hideaki Zama Hideaki Zama , Shunri Oda Shunri Oda
Published: February 2005

We have investigated the preparation of YBa2Cu3O
x
thin films on MgO (100) substrates by sequential metalorganic source supply with the metal configuration along the c-axis at low substrate temperature (560°C). Oxygen is also sequentially supplied to the substrate. Four types of films are prepared by various sequential supply patterns of metalorganic precursors and oxygen. Our results show that layer-by-layer oxidation is important for c-axis orientation of the films and that Ba is more suitable than Cu as the first layer with respect to preventing the growth of CuYO2.
Optical Detection of Transient Lamb Waves on Rough Surfaces by a Phase-Conjugate Method
Authors: Matsuda Yoichi , Hidetoshi Nakano Hidetoshi Nakano , Satoshi Nagai Satoshi Nagai
Published: February 2005

A convenient method is described for optically detecting Lamb waves on rough surfaces. A pulsed YAG laser excites Lamb waves, which are detected in a noncontact manner by a Michelson interferometer with a self-pumped phase-conjugate mirror. The present method automatically corrects the wavefront distortion caused by rough surfaces and also shows a flat spectral response over large bandwidths necessary for the analysis of the dispersion relationship. To illustrate the validity of the method, experimental results are presented for two kinds of thin plates.
Laser Emission from Dye-Doped Polystyrene Microsphere*
Authors: Kuwata-Gonokami Makoto , Takeda Kenji , Hiroaki Yasuda Hiroaki Yasuda , Kazuhiro Ema Kazuhiro Ema
Published: February 2005

Lasing of dye-doped polystyrene microspheres with diameters ranging from 10 µm to 92 µm is observed. Emission from an individual sphere placed on a glass plate is examined under optical pumping with nanosecond pulses whose frequency is tuned to the absorption band of the dye. Spectral and temporal responses, and spatial profile show the characteristics of lasing with spherical cavity modes.
Dependence of Resonance Frequency of a Membrane Vibrated Photothermally on Pressure and Geometry in a Low-Vacuum Region
Authors: Hane Seiki Inaba
Published: February 2005

An experimental study of resonance frequency for a membrane vibrated photothermally in a low-vacuum region is described. The resonance frequency is decreased by the reaction force from gases around the vibrating membrane. Experimental values of resonance frequencies for various types of rectangular membranes in several kinds of gases agree well with theoretical ones.
Number Fluctuation Laser Velocimeter with Single Aperture
Authors: Iwamoto Toshiyuki , Hanataka Shinya , Norio Ogita Norio Ogita , Kohji Ohbayashi Kohji Ohbayashi
Published: February 2005

Of the three terms in the photon correlation function of light scattered from particles suspended in a fluid flow illuminated by a laser beam, it has been pointed out that not only the self-beat term but also the number fluctuation term provides information about the velocity. Based on this fact, a number fluctuation laser velocimeter has been proposed. The principle of the method has been explained. Experimental procedures to make the number fluctuation signal dominant have been proposed, based on the property of the photon correlation function. Applications to pipe flows have been carried out to demonstrate capability of the method.
Step-Controlled Epitaxial Growth of 4H-SiC and Doping of Ga as a Blue Luminescent Center
Authors: Kimoto Tsunenobu , Yamashita Atsushi , Akira Itoh Akira Itoh , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Homoepitaxial growth of 4H-SiC could be achieved at 1500°C on off-oriented 4H-SiC{0001} substrates by means of a vapor phase epitaxial method. Grown layers showed specular smooth surfaces on both (0001)Si and (0001̄)C faces. Doping of Ga during crystal growth was carried out and photoluminescence of grown layers was studied. Bluish-violet photoluminescence due to donor(N)-acceptor(Ga) pair recombination and recombination of a free electron with a hole at a Ga acceptor was observed. The emission attributed to the latter recombination process became dominant at high temperatures above 100 K. The luminescence of Ga-doped 4H-SiC was not quenched up to temperatures as high as 150 K, whereas the luminescence intensity of Al-doped 6H-SiC and 4H-SiC started to decrease at 70 and 85 K, respectively.
Micromagnetic Computation of Damping Constant Effect on Switching Mechanism of a Hexagonal Platelet Particle
Authors: Uesaka Yasutaro , Nakatani Yoshinobu , Hayashi Nobuo
Published: February 2005

The effect of Gilbert's damping constant on the switching mechanism of a magnetic hexagonal platelet particle was investigated by computer simulation. Three damping constants were used for the calculation: α=1, 0.3 and 0.1. When a uniform field is applied in the direction of the easy axis of the platelet, the average magnetization in that direction begins to oscillate. The amplitude of the oscillation, which increases with decreasing damping constant, decreases with time. Switching occurs after the oscillation ceases. The magnetic moments of the platelets switch in the vortex mode for all damping constants investigated. The switching mechanism is complicated in a small α platelet; the center of the vortex moves around in a hexagonal plane at small α (α=0.1), but the center of the vortex stays at the center at large α (α=0.3, 1).
The Effect of Antimony Oxide on the Electrical Properties and Stability of ZnO Varistors
Authors: Shen Chi-Yen , Chen Ying-Chung , Wu Long
Published: February 2005

The nonlinear current-voltage characteristics, depression angle and stability of ZnO varistors were investigated as a function of valence and amount of antimony oxide. The nonlinear properties were improved, the depression angle decreased, and the stability under continuous dc bias increased with decreasing valence of the antimony ion. However, the nonlinear properties became worse with an increasing amount of antimony oxide for any valence. The relaxation time was insensitive to the valence of the antimony ion and the amount of antimony oxide, while the increased antimony oxide content enhanced the electrical stability as a function of time. Spinel particles formed by the reaction of antimony oxide and ZnO, were suggested as playing an important role in the improvement of electrical properties and stability by stressing the junction between two ZnO grains.
Etching Studies of Gel-Grown Crystals: (100) Faces of Potassium Dihydrogen Orthophosphate
Authors: Gupta Suparna Sen , Tanusree Kar Tanusree Kar , Siba Prasad Sen Gupta Siba Prasad Sen Gupta
Published: February 2005

Microscopic observations of the chemically etched prismatic (100) faces of single crystals of KDP (KH2PO4), grown from modified double diffusion gel technique, revealed the presence of hillocks and etch spirals. Both edge and screw dislocations were clearly identified with suitable etchants. Influence of various alcohols and acid concentration on the pit morphology has also been observed. The features have been presented and discussed mainly from examination of optical micrographs.
Fabrication of Langmuir-Blodgett Films with a Novel Amphiphilic Ferrate(III) Coordination Compound
Authors: Armand Franck , Okada Shuji , Yase Kiyoshi , Matsuda Hiro , Nakanishi Hachiro , Hirochika Sakuragi Hirochika Sakuragi , Katsumi Tokumaru Katsumi Tokumaru
Published: February 2005

A newly synthesized amphiphilic coordination compound, pentacyano(4-octadecylaminopyridine)ferrate(III) (POF), is shown to produce a stable Langmuir monolayer on pure water when the counter cation is chosen so as to enhance the hydrophobic character of this metal complex. Langmuir-Blodgett films were fabricated by means of the horizontal lifting method. Deposition up to 60 layers was confirmed by the linear increase in the charge transfer absorption of the films. The interlayer spacing measured by X-ray diffraction indicated a Y-type structure due to molecular overturn during the deposition process. Alternate deposition of POF and an amorphous polymer also gave centrosymmetric structure.
Self-Ordered Film of Hemicyanine Derivative Characterized by Phase-Sensitive Optical Second-Harmonic Generation
Authors: Sato Osamu , Baba Ryo , Kazuhito Hashimoto Kazuhito Hashimoto , Akira Fujishima Akira Fujishima
Published: February 2005

Second-harmonic generation coherent interferometry was applied to the characterization of the adsorbed layer of a hemicyanine derivative 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (DSM) on a fused silica plate. It was clarified that the DSM molecules on the substrate were self-aligned with their methylpyridinium group facing towards the hydrophilic silica substrate.
Properties and Surface Morphology of Indium Tin Oxide Films Prepared by Electron Shower Method
Authors: Yumoto Hisami , Hatano Jyun , Watanabe Tuneo , Sato Kazuhiro Fujikawa
Published: February 2005

Indium tin oxide (ITO) thin films were prepared by electron beam evaporation (EB) with an electron shower. Lawnlike and VLS (vapor-liquid-solid) whiskers of ITO were grown at 300°C on the surface of the film with and without the electron shower, respectively. The electron resistivity of the ITO film fabricated with the electron shower was 4×10-4 Ω·cm, which was one order of magnitude smaller than that prepared by the EB at the same substrate temperature (300°C). The electron shower activated the oxidation of In and Sn, but the film was oxygen deficient. The increasing crystallization of the oxygen deficient ITO film was the cause of the decreasing resistivity.
Electron Wave Transfer in Coupled Quantum Wires and Its Control by Externally Applied Electric Field
Authors: Nara Shigetoshi , Hara Yuji , Totsuji Hiroo , Nomura Yoshinori , Tsukada Noriaki
Published: February 2005

Quantum mechanical electron wave transfer between two quantum wires which are weakly coupled via a thin potential barrier is considered. The transfer efficiency is calculated analytically and numerically for several specified cases of geometrical structures, potential barrier heights and an externally applied electric field. Estimated transfer time is of the order of one picosecond in typical mesoscopic structures. The model in this paper can be used to determine important structure parameters for experiments on an electron directional coupler controlled by an external electric field.
Crystal Structure of TiN Film Fabricated by Reactive Sputtering on Si(100) Substrate
Authors: Tsuchida Masahiko , Kuroda Tsukasa , Iwakuro Hiroaki , Shimizu Takashi
Published: February 2005

The crystal structure of TiN film fabricated on a Si(100) surface by reactive sputtering was studied by means of X-ray diffraction. When the N2 flow rate was less than 0.058, hexagonal Ti was deposited. The [001] axis of Ti was normal to the substrate face. When the N2 flow rate was more than 0.091, cubic TiN was deposited. The [111] axis of TiN was normal to the substrate face.
A Simple Detector for Measuring the Density of Air Using an α-Ray Source
Authors: Shigeaki Matsumoto Shigeaki Matsumoto , Satoru Toyooka Satoru Toyooka
Published: February 2005

A simple detector, which consists of a radioactive α-ray source and a ZnS(Ag) scintillator connected with an optical fiber cable, was devised for measuring the density of air under atmospheric pressure. It was shown that the density of air could be measured with the rms error of ±4×10-6 g/cm3 in the range from 1.074×10-3 to 1.309×10-3 g/cm3.
Influence of Reaction Products on Si Gate Etching with a Photoresist Mask in HBr/O2 and Cl2/O2 Electron Cyclotron Resonance Plasma
Authors: Takashi Morimoto Takashi Morimoto
Published: February 2005

Highly directional and highly selective (Si/SiO2 and Si/photoresist) dry etching of Si metal-oxide-semiconductor (MOS) gates with a photoresist mask is achieved using electron cyclotron resonance (ECR) HBr/O2 etching reactions. In this process, the photoresist mask is coated with SiO2 in HBr/O2 plasma, and highly selective etching in Cl2/O2 plasma is combined with this SiO2 coating process. In the Cl2/O2 plasma, oxygen reacts with Si etching products such as SiCl
x
on the surface of both the Si and the coated SiO2, generating SiO2 which is deposited as a film on the coated SiO2. However, no deposition occurs on the etching surface of Si, and the Si etching rate increases. This result proves that the SiO2 coating protects the photoresist during Cl2/O2 plasma etching.
Characteristics of Platinum-Palladium Alloy Film for X-Ray Mirrors
Authors: Nakajima Kunio , Sudo Shuzo , Kanda Hideo , Ishii Takayuki , Aoki Sadao
Published: February 2005

Pt-Pd alloy films have been produced for X-ray mirrors by sputter deposition. The characteristics of the alloy films have been investigated with the aid of X-ray reflectivity measurement, the transmission electron microscope, X-ray diffraction and the atomic force microscope. The grain growth of the platinum film can be controlled by the addition of a small amount of palladium. As a consequence, there is a considerable decrease in surface roughness. Thus, a Pt-Pd film which is smoother and has higher reflectivity is obtained.
Microwave Ion Source Using Resonant Cavity
Authors: Tahara Hirokazu , Yasui Toshiaki , Onoe Ken-ichi , Yasuji Tsubakishita Yasuji Tsubakishita , Takao Yoshikawa Takao Yoshikawa
Published: February 2005

Ring-cusped magnetic-field ion sources using 2.45-GHz-microwave resonant cavities were studied to develop high-performance compact ion sources for economically assisting material processings. The minimum flow rate required to sustain discharge was 10 sccm for weak-B-field off-resonance discharge in the TM011-mode-excitation cylindrical cavity, 6 sccm for weak-B-field discharge in the reentrant coaxial cavity, in which a stronger electric field was generated compared with that in the cylindrical cavity, and 3 sccm for electron cyclotron resonance (ECR) discharge in the cylindrical cavity. As a result of ion beam extraction, the highest mass utilization efficiency of 18.7% was achieved for ECR discharge.
Dot Structures Fabricated by Laser Etching -Laser Wavelength Dependence of Dot Structures Fabricated by Laser Etching-
Authors: Ezaki Mizunori , Kumagai Hiroshi , Obara Koichi Toyoda
Published: February 2005

Submicron periodic dot structures on semiconductor substrates (n-InP, n-GaAs) were fabricated directly with the one-step laser-photochemical dry etching of n-InP and n-GaAs using a holographic exposure system. We employed a new etching technique which makes use of laser-induced surface electromagnetic waves (SEW) in the etching gas/semiconductor interface. The size of dot structures on n-InP was about 105 nm for the frequency-tripled Nd:YAG laser and 80 nm for the frequency-quadrupled Nd:YAG laser. Thus, the size of dot structures depended upon the incident laser wavelength.
Experimental Results on the Level Crossing Intervals of the Phase of Sine Wave Plus Noise
Authors: Youssef Neji , Munakata Tsutomu , Tadashi Mimaki Tadashi Mimaki
Published: February 2005

Experimental study was made on the level crossing intervals of a phase process of a sine wave plus narrow-band Gaussian noise. Since successive level crossings of phase do not necessarily occur alternately in the upward and downward direction due to the phase jump beyond 2π, the usual definitions of the probability densities of the level crossing intervals for continuous random processes are not applicable in the case of the phase process. Therefore, the probability densities of level crossing intervals of phase process are newly defined. Measurements of these densities were performed for noise having lowpass spectra of Gaussian and 7th order Butterworth types. Results are given for various values of the signal-to-noise power ratio and of the crossing level, and compared with corresponding approximation developed under the assumption of quasi-independence. The validity of the assumption depends on the spectrum shape of the noise.
Adsorption Structure of the Na-Saturated Si(100)2×1 Surface Studied by Field-Ion Scanning Tunneling Microscopy/Spectroscopy
Authors: Hashizume Tomihiro , Motai Kumi , Dong-Ryul Jeon Dong-Ryul Jeon , Toshio Sakurai Toshio Sakurai
Published: February 2005

The adsorption geometry of Na on the Si(100)2×1 surface has been investigated using field-ion scanning tunneling microscopy/spectroscopy (FI-STM/STS). The high resolution STM image of the Na-saturated surface showed a 2×1 dimerized structure, similar to that of the clean 2×1 surface. Individual dimers were bifurcated in the filled state STM images, resembling to those of the empty state images for the clean surface. The STS data for this surface showed a large energy band gap of approximately 1 eV, suggesting that the Na/Si(100)2×1 surface was semiconductor-like. These observations are consistent with the results of Kono's group and a recent theoretical study by Terakura's group, supporting the double-layer model for Na on the Si(100)2×1 surface.
Roughness Evaluation of Thermally Oxidized Si(111) Surfaces by Scanning Force Microscopy
Authors: Suzuki Mineharu , Homma Yoshikazu , Yukie Kudoh Yukie Kudoh , Norikuni Yabumoto Norikuni Yabumoto
Published: February 2005

We used scanning force microscopy to evaluate the surface roughness of thermally oxidized Si(111). The initial surface, before oxidation, consisted of atomically flat terraces containing monoatomic steps and stepbands. The morphology of 10-nm-thick oxide surfaces formed at 800 to 1200°C was roughly similar to that of the initial surface. It is also revealed that a monoatomic step was retained on a 100-nm-thick oxide layer formed at 1100°C. The surface roughness tended to decrease as the oxidation temperature increased.
C60 and Beyond: From Magic Numbers to New Materials
Authors: Klaus Sattler Klaus Sattler
Published: February 2005

C60 is the first `magic number' cluster which has been produced in large enough quantities to be accumulated as a solid. We will discuss some of the outstanding properties of such clusters and their potential for the generation of new materials.
Reaction Mechanism of Mercury-Sensitized Photochemical Vapor Deposited Silicon Oxide
Authors: Lan Wen-How , Lin Wen-Jen , Tu Shun-Lih , Huang Sheng-Jenn Yang
Published: February 2005

The deposition mechanism for silicon oxide (SiO
x
) films grown by the mercury-sensitized photochemical vapor deposition (photo-CVD) method using silane (SiH4) and nitrous oxide (N2O) under irradiation of a low-pressure mercury lamp has been studied. An increasing-naximum-decrease pattern of the deposition rate with increasing silane partial pressure ratio (P
s=P
SiH4/P
total) has been observed. Deposition rates for the SiO-like and SiO2-like films have been analyzed based on the Langmuir-Hinshelwood surface reaction theory. Rate equations were also derived. By means of the Arrhenius plots, activation energy of the surface reaction and the heat of adsorption can be determined.
Direct Photochemical Vapor Deposition of Hydrogenated Amorphous Silicon -Effects of Excitation Wavelengths and Source Gases-
Authors: Shirafuji Tatsuru , Nakajima Sagara , Wang Yun Fen , Takeshi Genji Takeshi Genji , Kunihide Tachibana Kunihide Tachibana
Published: February 2005

Hydrogenated amorphous silicon films have been prepared by a direct photochemical vapor deposition method using different excitation wavelengths and source gases. The films deposited with the combination of Si2H6+147 nm and Si2H6+185 nm showed good properties indicated by low value of Si-H2 bond density, Urbach energy and defect-state density compared with the films deposited with SiH4+147 nm. Results of simulation demonstrated that these good properties are caused by the smaller contribution of SiH2 and larger contribution of monoradicals to the deposition, and that interconnection of surface sites created from SiH2 is difficult compared with that from monoradicals. Detailed analysis of the simulation revealed that the reactions which control radical density are not those of initial photolysis but instead are secondary reactions, such as those involving atomic hydrogen.
Possible New Mechanism of Acceptor Character for Oxygen in ZnSe and Other II-VI Semiconductors
Authors: Charles Robert Helms Charles Robert Helms
Published: February 2005

In this paper a new model for the p-type doping of ZnSe by oxygen is suggested based on the Zn/Se/O phase diagram and crystallographic considerations. It is shown that the characteristics of the oxygen may be determined by whether the ZnSe is grown “Zn rich” or “Se rich”. This may explain why this effect is hard to reproduce from laboratory to laboratory. In the range of proper stoichiometry the oxygen can not only act as an acceptor but may compensate Zn interstitial donor native defects in the ZnSe.
Electrical Conductivity of Benzoylferrocene in Presence of Adsorbed Vapors
Authors: Ashis Bhattacharjee Ashis Bhattacharjee , Biswanath Mallik Biswanath Mallik
Published: February 2005

Enhancement in the dark conductivity of benzoylferrocene upon adsorption of different organic vapors has been studied with the help of sandwich cell technique. Plot of dark conductivity vs temperature shows conductivity peak(s). The position of the peaks as well as the intensity have been found to depend on the amount as well as the nature of adsorbed vapor. In presence of adsorbed vapors, this material shows a very high value of activation energy (E) and the pre-exponential factor (σ0) in the usual semiconduction equation [σ=σ0exp (-E/2kT)]. Existing theories for adsorption-induced change in the electrical conductivity of materials are not suitable for explaining the observed results. Possible reasons for the adsorption-induced changes in the conductivity behavior have been discussed.
Synthesis and Characterization of Ba β-Diketonate Complexes for Chemical Vapor Deposition of Thin-Film Superconductors
Authors: Sato Rikiya , Takahashi Koji , Yoshino Masao , Kato Hiroshi , Ohshima Shigetoshi
Published: February 2005

The synthetic condition and thermal properties of Ba(DPM)2 (bis-dipivaloylmethanato-barium), Ba(DIVM)2 (bis-diisovalerylmethanato-barium), and Ba(DBM)2 (bis-dibutyrylmethanato-barium) were investigated. It was found from NMR analysis that ligands of DPM, DIVM and DBM could be prepared as intended. The yield values of Ba(DIVM)2 and Ba(DBM)2 were about three times larger than that of Ba(DPM)2. It was clarified from thermal properties measured using thermogravimetry (TG) that volatilization of Ba(DPM)2 was higher than that of Ba(DIVM)2 and Ba(DBM)2, however, melting points of Ba(DIVM)2 and Ba(DBM)2 were slightly lower than that of Ba(DPM)2. The volatilization of Ba(DPM)2, Ba(DIVM)2 and Ba(DBM)2, exposed to the air for only one week, decreased. The stability of Ba(DPM)2(Phen)2, Ba(DIVM)2(Phen)2 and Ba(DBM)2(Phen)2, which were prepared by addition of phenanthroline to Ba(DPM)2, Ba(DIVM)2 and Ba(DBM)2, was superior to that of mother barium chelates.
YBCO-BiO Composite Superconductor for Granular-Type Josephson Microwave Detector
Authors: Takai Minoru , Ikemachi Takaaki , Niki Kazuya , Yoshikawa Shuichi , Yamano Kohji , Yorinobu Yoshisato Yorinobu Yoshisato , Shoichi Nakano Shoichi Nakano
Published: February 2005

We have developed a new YBCO-BiO composite superconductor for granular-type Josephson microwave detectors. This composite superconductor was prepared by doping YBa2Cu3O
x
with Bi2O3 and it was found that the normal state resistance increased with the amount of Bi2O3 doping up to 15 wt.%, without deterioration at the zero-resistance temperature. BaBiO3 was segregated at the interface of the YBCO particles during sintering at a temperature of about 940°C. This seemed to enhance the resistance of the grain boundary and improve the microwave detection responsivity. Practical responsivity (R
Mv) of 180 V/W and noise equivalent power (NEP) of about 1.4×10-14 W/√Hz were obtained using a YBCO-BiO detector with 15 wt.% Bi2O3 doping.
Influence of Rare Earth Ions on BaO-TiO2-Rare Earth Oxide Ceramics for Microwave Applications
Authors: Fukuda Koichi , Fujii Itsuhiro , Kitoh Ryozo , Cho Yasuo , Awai Ikuo
Published: February 2005

The dielectric ceramic materials, 0.143BaO-0.714TiO2-0.143 rare earth oxides (REO
x
), have unique dielectric properties at microwave frequencies, which depend on the rare earth element (RE=Pr, Nd, Sm). In order to study the effect of the rare earth ions on dielectric properties, infrared reflection spectra of these ceramics were measured from 50 to 4000 cm-1 at room temperature. These data were analyzed according to the model proposed by Gervais and Piriou. Also, the fourth-order dielectric constants of these materials were estimated for the purpose of investigating the relationship between the dielectric loss and the anharmonic terms in the potential energy.
Noncrystalline Condensation of Densely Dissolved Optically Nonlinear Organic Compound in Polymer Matrices
Authors: Hiraga Takashi , Tanaka Norio , Hayamizu Kikuko , Mito Akihiro , Takarada Shigeru , Yamasaki Yuuichi , Nakamura Michie , Hoshino Nobuo , Tetsuo Moriya Tetsuo Moriya
Published: February 2005

Optical properties and condensed states of the densely dissolved
optically nonlinear organic compound in polymer matrices were investigated
by means of optical measurements, structural analysis and pressure tuning
spectroscopy. In the investigation of the absorption peak wavelength,
2-methyl-4-nitroaniline (MNA) in poly(methyl methacrylate) (PMMA)
exhibited characteristics
intermediate between the crystal and the MNA dissolved in solvents, i.e.,
noncrystalline condensation. This result was consistent with those of X-ray
diffraction analysis, second- and third-harmonics generation, IR absorption and
13C-NMR spectroscopies. It has also been revealed that such a system
provides the most suitable measuring method of the third optical nonlinear
constant for a variety of compounds.
Quasi-Static and Dynamic Density Fluctuations in the Glassy State. I. Speckle Patterns and Background Scattering
Authors: Tomoyoshi Yamashita Tomoyoshi Yamashita , Kensuke Kamada Kensuke Kamada
Published: February 2005

It has been clarified for the first time that the light scattering profile of amorphous matter, e.g., polymethylmethacrylate (PMMA) and quartz glass, in the glassy state displays two aspects in precise light scattering measurements in which optical resolution power is enhanced for a scattering angle. One aspect is of many needle-like spiky patterns termed “speckle” resulting from the random interference of scattered waves due to frozen-in density fluctuation. The other is background scattering (incoherent scattering) showing beneath the speckle patterns, which is caused by the dynamic density fluctuation of atomic and molecular motion with a relaxation time much shorter than our observation time scale. It was found that the amount of background scattering of PMMA unexpectedly reached about half of V
v scattering intensity, in spite of the room temperature being much lower than T
g. The glassy state is interpreted to be a linear system in which quasi-static and dynamic density fluctuations coexist.
Crystal Growth of Bi4Ge3O12 and Heat Transfer Analyses of Horizontal Bridgman Techniques
Authors: Kawano Katsuyasu , Yoshida Toshiyuki , Nakata Ryouhei , Noboru Yamada Noboru Yamada , Minoru Sumita Minoru Sumita
Published: February 2005

Nonhygroscopic, high-radiation-absorptivity scintillation crystals of BGO (bismuth germanate: Bi4Ge3O12) have been grown by the horizontal Bridgman (HB) method using very sharply focused gas jets as the heat source. It was determined by means of optical and X-ray characterization that the crystal growth had been performed successfully. On the basis of a one-dimensional time-dependent heat transfer model, simulation analyses have been used to examine the validity of this method under various growth conditions: temperature distribution, locations of the boundaries between the crystal, melt and polycrystal components, and growth rates.
Diffusion of Point Defects in Silicon Crystals during Melt-Growth. I -Uphill Diffusion-
Authors: Habu Ryuichi , Yunoki Isamu , Saito Takao , Tomiura Azusa
Published: February 2005

We present experimental results which show that the critical growth rate at which the OSF (oxidation induced stacking fault)-ring of CZ (Czochralski)-silicon single crystal contracts and disappears into the center of the crystal does not depend on the crystal diameter. To explain this phenomenon, the uphill diffusion of point defects toward the crystal growth interface was introduced in addition to normal diffusion. The diffusion behavior of point defects at the growth end of the crystal is found to be sensitively dependent upon the growth rate of the crystal. When the growth rate is low, the effect of uphill diffusion is greater than that of normal diffusion. Then, the out diffusion of point defects is not dependent upon the crystal radius. When the growth rate is high, point defects must diffuse out of the crystal through the crystal surface via normal diffusion.
Tungsten Films with the A15 Structure
Authors: Masashi Arita Masashi Arita , Isao Nishida Isao Nishida
Published: February 2005

Influence of the atmosphere on the crystal structure of thin tungsten films produced by the evaporation method in vacuum was studied. While the crystal structure of the films produced in a high vacuum (e.g., 10-6 Pa) was bcc, the films took on an A15 structure in oxygen and nitrogen atmospheres (e.g., 10-4 Pa). This phenomenon did not occur with the introduction of inert gases such as helium and argon.
Behavior of Al on Clean and Oxidized GaAs(110) Surfaces
Authors: Hyunwoo Kim Hyunwoo Kim
Published: February 2005

The adsorption of Al on clean and oxidized GaAs(110) surfaces was studied. The characteristics of an oxide surface formed in vacuum and during the chemical etching process of the tip have been investigated using the field desorption (FD) cleaning method and the retarding potential analyzer (RPA) equipped with an argon laser. The results obtained for the FD clean surface and on the oxidized surface are discussed in terms of the RPA threshold and work function change. The oxide films formed at relatively low temperatures on the GaAs(110) surface can easily be desorbed by FD. The intrinsic potential drops across the oxide surface disappear suddenly at a certain field value. This may indicate that the desorbed surface region is composed of a metallic species such as Ga. Changes in work function are observed but there is no change in the threshold values (V
th) with deposition of Al on the field-desorbed clean surface. The thick layers of Al on the oxidized surface completely cancel the effect of oxide on V
th, which decreases to the value of a metallic clean surface. In addition, the value of V
th decreases dramatically to that of a metallic clean surface by absorption of the laser beam on the oxidized surface, whereas only the thermal effect is seen on a metallic clean surface.
High-Temperature Scanning Tunneling Microscopy Observation of a (15, 17, 1) Facet Structure on a Si(110) Surface
Authors: Yamamoto Youiti , Sueyoshi Takashi , Tomoshige Sato Tomoshige Sato , Masashi Iwatsuki Masashi Iwatsuki
Published: February 2005

High-temperature scanning tunneling microscopy (HTSTM) was applied to observe a facet structure on a Si(110) surface. The facet structures of (15, 17, 1) and (17, 15, 1) and the 16-structure were observed at 655°C. The 16-structure was formed on flat parts. It was confirmed that the 16-structure and the facet structures of (15, 17, 1) and (17, 15, 1) coexisted on the surface on which hillocks are dispersed. The hillock may be a contamination.
Modifications of Polypropylene Induced by the Implantation of Iodine Ions
Authors: Hnatowicz Vladimír , Havránek Vladimír , Kvítek Jiří , Pe\vrina Vratislav , Švorčík Václav , Rybka Vladimír
Published: February 2005

The polypropylene (PP) samples implanted with I+ ions at the implantation energies of 50, 100 and 150 keV to the fluence of 1×1015 cm-2 were studied using standard RBS (Rutherford backscattering) technique. The surface of the implanted PP samples is heavily damaged and enriched in carbon. The measured projected ranges of iodine atoms are by 10 to 30% lower than the theoretical ones calculated using Monte-Carlo simulation code TRIM (transport of ions in matter) code for pristine PP. The differences may be due to structural changes of polymer during the ion implantation. The range stragglings exceed the theoretical TRIM estimations about twice. The profile broadening is probably due to the diffusion of the iodine atoms through the damaged PP surface layer. In repeated RBS measurements, the iodine diffusion was confirmed with diffusion coefficient of 2.7×10-18 cm2·s-1. Noticeable oxidation of the implanted samples was observed, with majority of the oxygen atoms being trapped in the region of maximum radiation defects. The bulk oxygen concentration profile resembles that of iodine but it is shifted inward by 200-350Å. The relative oxygen content in the bulk is an increasing function of the implantation energy and it exceeds considerably the stoichiometric value for common iodine oxides.
Number Fluctuation Laser Velocimeter with Two Apertures
Authors: Ogita Norio , Kanda Toshikazu , Toshiyuki Iwamoto Toshiyuki Iwamoto , Kohji Ohbayashi Kohji Ohbayashi
Published: February 2005

In the photon correlation function of light scattered from particles suspended in a flow, not only the self-beat term but also the number fluctuation term carries information about the velocity. Based on this fact, a number fluctuation laser velocimeter with two observation apertures has been proposed. The principle of the method is explained. Applications to pipe flows have been carried out to demonstrate the capability of the method, and that it is particularly suited for quantitative characterization of turbulence as well as velocimetry.
Surface Effects on Leakage Current and Lifetime in Pt Diffused Planar Silicon p+n Diodes
Authors: Pahlawan Sagala Pahlawan Sagala , Chang Shu Chang Shu , Hiroshi Kuwano Hiroshi Kuwano
Published: February 2005

The diffusion of platinum into gate-controlled silicon p
+
n diodes is carried out at a temperature ranging from 800 to 1000°C for 40 min to investigate the effects of Pt diffusion on leakage current and lifetime in conventional planar silicon p
+
n diodes with the metal oxide semiconductor structure. From the measurement of I-V (current-voltage) characteristics and the reverse recovery time with various gate voltages, it is revealed that the surface covered with oxidized silicon has a significant effect on the leakage current, but no recognizable effect on the lifetime. It is found that the dominant generation centers in the p
n junction and recombination centers in the bulk are at the same level, located at Ec -0.52 eV.
The Effects of Polishing Damage and Oxygen Concentration on Gate Oxide Integrity in Silicon Crystals
Authors: Kato Takao Abe
Published: February 2005

The gate oxide integrity (GOI) of FZ crystals is independent but the GOI of CZ crystals is strongly dependent on the polishing conditions which means whether mechanical or chemical components are dominant. The GOI of CZ crystals is clearly improved by etching of surface layers, that is, 0.5 µm in depth by mixed acid and 0.04 µm by NH4OH/H2O2solution. MCZ crystals with low concentration of oxygen (∼10 ppma) always show higher GOI yields than CZ crystals with high concentration of oxygen (∼18 ppma). The above etching effects suggest that the polishing damages existing in as polished surfaces cause the GOI degradations together with the oxygen atoms in silicon crystals.
Direct Evidence for a Charge-Controlled Optical Quenching of EL2 Centers in Semi-Insulating GaAs
Authors: Ohyama Tyuzi , Shimizu Tetsuo , Hiromi Kobori Hiromi Kobori , Eizo Otsuka Eizo Otsuka
Published: February 2005

We present results of microwave photoconductivity as well as far-infrared laser magnetooptical absorption measurements obtained for LEC (liquid encapsulated Czochralski)-grown semi-insulating GaAs crystals. At low temperature we have observed a “photo-quenching effect” both for signals of microwave photoconductivity and for the shallow donor Zeeman absorption measured using a far-infrared laser, under the condition of BBG (below-band-gap) photoexcitation. Through these experimental observations, we conclude that the shallow donor is associated with the metastable state of the EL2 center in LEC-grown semi-insulating GaAs. From the temperature dependence of microwave photoconductivity decay with BBG pulsed photoexcitation, we can estimate the characteristic activation energy, ΔE
A=240 meV, which originates from a barrier in the conduction band related to the Franck-Condon shift of the EL2 metastable state.
Thin-Film Transistors with Polycrystalline Silicon Prepared by a New Annealing Method
Authors: Nam Kee-Soo , Song Yoon-Ho , Baek Jong-Tae , Kong Hong-Jin , Lee Sang-Soo
Published: February 2005

A new annealing method, nucleation by rapid thermal annealing (RTA) and grain growth in furnace annealing, has been developed to obtain high-quality polycrystalline silicon (poly-Si) and to reduce the long annealing time for solid-phase crystallization (SPC) of amorphorus silicon (a-Si) film without a decrease in grain size. Poly-Si thin-film transistors (TFTs) were fabricated using this method and the electrical properties of poly-Si film were evaluated. We obtained higher field effect mobility (25 cm2/(V·s)) and better uniformity (≤5% in 5-inch wafer) than those obtainable by the conventional furnace annealing.
Direct Observation of Crystallization Process from Amorphous Y-Ba-Cu-O Film by means of Optical Microscopy
Authors: Hoshizaki Hiroki , Shinohara Toshiyuki , Suzuki Masanobu , Enami Hiroyoshi , Imura Nobuaki Kawahara
Published: February 2005

Crystallization processes from amorphous Y-Ba-Cu-O films, i.e., the polycrystal formation by solid-state reaction below melting point and the crystal growth from the melt, were directly observed and analyzed by means of high-temperature optical microscopy.
Temperature and Rate-Dependent Measurements in Micromagnets*
Authors: Huei Li Huang Huei Li Huang , Ivo Klik Ivo Klik
Published: February 2005

An analytic description of hysteresis curves of single-domain noninteracting uniaxial particles is obtained taking into account forward and backward scattering processes. The curves from the equilibrium state of magnetization always switch at zero coercivity; those of nonequilibrium states of magnetization exhibit properties that bear good resemblance to the experimentally observed features of the temperature-, activation-volume and sweep-rate-dependent measurement of coercivities, increasing with the sweep rate and decreasing with temperature. Possible extension of the present theory is indicated.
Giant Magnetoresistance in Cu-Co Alloys Produced by Liquid Quenching
Authors: Kataoka Noriyuki , Endo Hiroshi , Shimada Kazuaki Fukamichi
Published: February 2005

Giant magnetoresistance (GMR) in Cu-Co alloys produced by liquid quenching has been confirmed. A supersaturated solid solution was obtained in a quenched state and fine-grained magnetic precipitates in fcc Cu-rich matrix were obtained upon annealing. It has been found that Cu80Co20 alloy annealed at 500°C for 1 h exhibits a giant magnetoresistance ratio as large as 4% at room temperature.