bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Soft X-Ray Emission from Al Plasma by Pulse Train Laser Irradiation
Authors: Hirose Hideo , Hara Tamio , Ando Kozo , Fumiko Negishi Fumiko Negishi , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: February 2005

A novel technique of effectively producing highly charged ions in laser produced plasma is demonstrated. Time-resolved and integrated soft X-ray spectra showed that ionization of Al atoms is greatly promoted up to Al10+ through the use of a pulse train laser even at very low peak power (1011 W/cm2). The X-ray conversion efficiency increased with increasing number of pulses and with decreasing interpulse time. The interpretation of our experimental results is presented.
Deoxidization of Carbon Dioxide by Pulse Power Discharge
Authors: Nakagawa Yoshiro , Nishitani Akito Kohchi
Published: February 2005

Carbon dioxide was effectively reduced to carbon monoxide by pulse power discharge. Linear discharge in a glass tube filled with CO2 or CO2 and H2 gas mixture at 150 to 450 Torr pressure was powered by a low-impedance Marx generator (about 3 Ω, 200 kVmax, stored energy, 10 kJ). The maximum reduction efficiency was 290 nmol/sW (the electric power used in the estimation was the stored energy in capacitors of the Marx generator).
Appearance of Single-Crystalline Properties in Fine-Patterned Si Thin Film Transistors (TFTs) by Solid Phase Crystallization (SPC)
Authors: Takashi Noguchi Takashi Noguchi
Published: February 2005

Uniformity of thin film transistor (TFT) characteristics was evaluated by varying the channel size. As channel length decreased and width fell below 1 µm, uniformity was degraded drastically. A few samples showed high-performance characteristics such as sharp gate voltage swing below 100 mV/dec and high mobility as high as 100 cm2/V·s near room temperature. Upon evaluation of their temperature dependence, the conduction mechanism showed not polycrystalline but single-crystal-like properties in the lattice scattering. The improved TFTs are thought to have been formed in grain boundary-free crystal grains.
High-Tc(Bi, Pb)2Sr2Ca2Cu3O10 Superconducting Magnet Operated Using 20 K Gifford-McMahon-Type Refrigerator
Authors: Ohkura Kengo , Mukai Hidehito , Hikata Takeshi , Ueyama Munetsugu , Kato Takeshi , Jun Fujikami Jun Fujikami , Ken-ichi Sato Ken-ichi Sato
Published: February 2005

The conduction-cooled high-T
c (Bi, Pb)2Sr2Ca2Cu3O10 superconducting magnet has been successfully operated using a Gifford-McMahon-type (GM) refrigerator. The magnet continuously generates a magnetic field of 1 T inside a 40 mm bore with a coil temperature of 20 K while held in a vacuum for over 100 hours. The coil is wound using a reacted Ag-sheathed 61-multifilamentary tape which has already been found to have excellent bending properties.
Dielectric Constants of Surface-Stabilized Ferroelectric Liquid Crystals with Chevron and Quasi-Bookshelf Structures
Authors: Yudasaka Masako , Kazuya Nagao Kazuya Nagao , Takamasa Harada Takamasa Harada
Published: February 2005

Dielectric constants at frequencies less than 103 Hz of surface-stabilized ferroelectric liquid crystals with the quasi-bookshelf structures were smaller than those with the chevron structure. Externally applied DC electric fields monotonously decreased the dielectric constants of SSFLC with the chevron structure at frequencies less than 103 Hz but not those of the quasi-bookshelf structure. The DC electric fields did not change the electrooptical responses of the chevron structure but markedly improved those of the quasi-bookshelf structure.
Observation of Reconstructed Pt(100) Surface by Reflection Electron Microscopy
Authors: Akita Tomoki , Masaki Takeguchi Masaki Takeguchi , Ryuichi Shimizu Ryuichi Shimizu
Published: February 2005

A Pt(100) surface with stabilized reconstructed domains on a small single-crystalline sphere was prepared in an ultrahigh-vacuum (UHV) chamber with very good reproducibility and observed under reflection electron microscope (REM). Reconstruction of the structure with fivefold periods was confirmed by reflection high-energy electron diffraction (RHEED) and the reconstructed domains were observed by REM. The domains have also revealed fivefold superlattice fringes which were stable even under electron beam irradiation.
Large-Area Electron Cyclotron Resonance Plasma Source with Permanent Magnets
Authors: Shida Noriyoshi , Inoue Takashi , Kokai Hideki , Sakamoto Yuichi , Miyazawa Wataru , Den Shoji , Hayashi Yuzo
Published: February 2005

A large-area electron cyclotron resonance (ECR) plasma is generated by using permanent magnets and applying the whistler-mode launching of microwaves. A uniform plasma is produced with the uniformity of ±3.5% over 20 cm and ±1.8% over 16 cm in diameter; the plasma space potential is about 17 V with the uniformity of ±1% over 20 cm. The maximum ion current density is about 11.5 mA·cm-2. The purity of the produced plasma is high. No damage was found after the operation for 100 h with the microwave power of 600 W.
Development of Newly Designed Polarizer for High-Power Laser
Authors: Motokoshi Shinji , Yoshida Hidetsugu , Yoshida Kunio , Sadao Nakai Sadao Nakai
Published: February 2005

A multilayer thin-film polarizer with high damage resistance has been developed by adopting a new coating design that minimizes the induced electric field intensity within the multilayer coating. The damage threshold was ≥11 J/cm2 for the p-polarized incident beam from the coating side and ≥17 J/cm2 for the s-polarized backward-reflected beam from the substrate side for a 1.053 µm laser with a pulse width of 1 ns.
Enhancement of Emission Efficiency in Electroluminescent Diode Utilizing Vapor-Deposited Poly(alkylfluorene)
Authors: Ohmori Yutaka , Uchida Masao , Morishima Chikayoshi , Akihiko Fujii Akihiko Fujii , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

An electroluminescent diode utilizing vapor-deposited poly(alkylfluorene) has been demonstrated. Efficiency of electroluminescence has been increased by using vapor deposition of poly(alkylfluorene) as an emitting layer. A three layered structure of poly(alkylfluorene) diode has been fabricated using the vapor deposition technique. The energy band diagram is discussed for the layered structure of the diode.
Optical Absorption of Gas Phase C60 and C70
Authors: Kataura Hiromichi , Irie Norikazu , Kobayashi Nobuo , Achiba Yohji , Kikuchi Kouichi , Takaaki Hanyu Takaaki Hanyu , Shigeo Yamaguchi Shigeo Yamaguchi
Published: February 2005

We have measured optical absorption spectra of gas phase C60 and C70 from 1.9 to 6.5 eV at various temperatures up to 1000 K. The optical density spectra of C60 and C70 have only three and six peaks, respectively, in the measured spectrum range and can be reconstructed successfully with the same number of Lorentz oscillators. This simple spectrum structure suggests a simple view for the electronic state of a C60 molecule. We have estimated sublimation heats of C60 and C70 at 1.7 and 1.3 eV, respectively, from changes of absorption intensities with temperature.
Photoreflectance Study of CuAlSe2 Heteroepitaxial Layers
Authors: Shirakata Sho , Chichibu Shigefusa , Matsumoto Satoru , Shigehiro Isomuraod Shigehiro Isomuraod
Published: February 2005

Photoreflectance (PR) spectra have been measured on the CuAlSe2 epitaxial layers grown on GaAs(100), GaAs(111)A and GaP(100) substrates by means of the metalorganic chemical vapor deposition technique. The PR spectra showed strong dependence on the substrate, reflecting the orientation of the epitaxial layer. The results have been well explained from the polarization selection rule with the aid of X-ray measurements. Stress in the epitaxial layer is discussed in terms of the crystal field splitting of the valence bands.
Observation of Deep Level in p-n Junction Diode of 6H:SiC
Authors: Ashraf Uddin Ashraf Uddin , Tsutomu Uemoto Tsutomu Uemoto
Published: February 2005

We have investigated the deep level trap centers in a p-n junction diode of 6H:SiC by deep level transient spectroscopy (DLTS) measurements. An electron trap center 0.71 eV below the conduction band edge is observed for the first time in 6H:SiC. The estimated trap center concentration and its capture cross section are found to be around 2×1015 cm-3 and 5×10-14 cm2, respectively. The trap center concentration profile is found to be uniform. The origin of trap centers is suggested.
Unique Electrical and Optical Properties of Conducting Polymeric Liquid Crystal
Authors: Yoshino Katsumi , Yin Xiao Hong , Morita Shigenori , Nakazono Masahiro , Kawai Tsuyoshi , Ozaki Masanori , Jin Sung-Ho , Choi Sam-Kwon
Published: February 2005

Electrical conductivity of poly(bis(4-methoxy-4'-hexyloxy biphenyl)-dipropargyl malonate) (PMHBDPM) exhibits unique temperature dependence corresponding to the phase transitions. Thermochromism and solvatochromism are not observed in PMHBDPM. However, unique electrochromism has been observed. That is, with increasing doping level, PMHBDPM changes color from red in the non-doped state to colorless and then to blue in the highly doped state. Not only the conjugated main chain, but also the biphenyl unit in the side chain, are thought to play roles in the doping phenomenon. ESR (electron spin resonance) spin density as well as linewidth changed markedly with electrochemical doping. These characteristics have been discussed in terms of the soliton model.
Thermally-Induced Transformation of Phthalocyanine Microcrystals into Monomers in Polyamic Acid Film Prepared by Vapor Deposition Polymerization
Authors: Sakakibara Youichi , Hirofumi Matsuhata Hirofumi Matsuhata , Toshiro Tani Toshiro Tani
Published: February 2005

Using a vacuum method, copper phthalocyanine (CuPc) is dispersed in a polyamic acid film; CuPc is codeposited during the synthesis of the polymer by vapor deposition polymerization. In the film, CuPc is dispersed dominantly as α-form microcrystals within the polymer matrix. By heat treatment at 200°C in air, the microcrystals are crushed into much smaller pieces–considerablely into monomers. We conclude that this crushing is induced by the morphological change of the matrix polymer through the imidization reaction.
Heteroepitaxial TiN Films Grown by Reactive Ion Beam Epitaxy at Room Temperature
Authors: Kawakubo Takashi , Kenya Sano Kenya Sano , Michihiro Oose Michihiro Oose
Published: February 2005

Reactive ion beam epitaxy with an extra-low energy N2
+ ion beam and a Ti molecular beam has been employed to grow hetero-epitaxial TiN films on MgO substrates. The TiN film quality drastically depends on the N2
+ kinetic energy. Epitaxial TiN films with a low resistivity about 16 µΩ·cm were obtained at a kinetic energy of 50 eV/atom even at room substrate temperature, which is the lowest epitaxial temperature so far. At an elevated temperature, epitaxial growth was observed at a wide kinetic energy range. Epitaxial growth mechanisms in low energy reactive ion beam deposition are discussed.
Single Particle Relaxation Times from Shubnikov-de Haas Oscillations in Antidot Structures
Authors: Takahara Junichi , Gamo Kenji , Namba Susumu , Takaoka Sadao , Murase Kazuo
Published: February 2005

Magnetotransport of a two-dimensional electron gas system with a hexagonal array of antidots has been investigated. Single particle relaxation times of the two-dimensional electron gas system are determined by Landau level broadening. Two values of the time are observed in Shubnikov-de Haas oscillations in high and low fields. The critical field which separates between the two relaxation times corresponds to the field at which edge states around antidots begin to be formed.
Reproducible and Controllable Contact Electrification on a Thin Insulator
Authors: Morita Seizo , Fukano Yoshinobu , Uchihashi Takayuki , Okusako Takahiro , Sugawara Yasuhiro , Yamanishi Yoshiki , Oasa Takahiko
Published: February 2005

The mechanism of contact electrification on an insulator is one of the oldest problems in physics. The major problem is the lack of reliable data on the contact electrification and its dissipation, because of poor experimental reproducibility on even the sign of the contact electrified charge. Here we report a novel microscopic method with a bias voltage to obtain reproducible and controllable contact electrification on a thin insulator, and the first experimental result on the dissipation of the contact electrified charge.
Improvement of Pattern and Position Accuracies by Multiple Electron Beam Writing for X-Ray Mask Fabrication
Authors: Aya Sunao , Marumoto Kenji , Hideki Yabe Hideki Yabe , Yasuji Matsui Yasuji Matsui
Published: February 2005

To study the improvement of position and line-width accuracies of resist patterns for X-ray masks, we tried to examine multiple writing with an electron beam (EB) exposure system. First, the uncertainty of the position measurement is checked and reduced to 0.03 µm (3σ) by the short-length measurement method. Then, it is found that by increasing the number of writing times from one to four, the overlay accuracy is improved from 0.04 µm to 0.02 µm (3σ) and the line-width of the pattern is exactly controlled. These results show that sub-quarter-micron patterns are formed by the multiple-writing method with the present EB machine.
The Resistivity Measurements of HgBa2Ca2Cu3O8+x and HgBa2Ca3Cu4O10+x Superconductors under High Pressure
Authors: Ihara Hideo , Hirabayashi Masayuki , Tanino Hiroshi , Tokiwa Kazuyasu , Ozawa Hirotomo , Akahama Yuichi , Kawamura Haruki
Published: February 2005

The superconductivity of the HgBa2Ca2Cu3O8+x
(1223) and HgBa2Ca3Cu4O10+x
(1234) phases was studied by resistivity measurements under high pressure. The highest onset T
c (T
co) was 156 K at 25 GPa for a 1223 and 1234 mixed-phase sample and 140 K at 13 GPa for a 1223-phase sample. The T
co decreased after the maximum point with the increase of pressure.
Cluster Size and Shape Effects on Giant Magnetoresistance of Evaporated Co-Ag Alloy Films
Authors: Daisuke Miyauchi Daisuke Miyauchi , Satoru Araki Satoru Araki
Published: February 2005

Magnetoresistive (MR) and magnetic properties of Co-Ag alloy films evaporated in ultrahigh vacuum were studied. The measured MR ratios were 24.7% at room temperature (RT) for Co40Ag60 (at%) alloy film and 48.6% at 77 K for Co32Ag68 alloy film. In addition, the MR profile shows an anistropy between two applied field directions, transverse and normal to the current in plane. This anisotropy is caused by the pancake-shaped Co clusters.
Frequency Recovery and Pulse Compression Using Brillouin-Enhanced Four-Wave Mixing in an Iodine Laser
Authors: Choi Byoung Il , Min Sik Jo Min Sik Jo , Chang Hee Nam Chang Hee Nam
Published: February 2005

Brillouin-enhanced four-wave mixing (BEFWM) in CS2 has been investigated experimentally using an iodine laser. The output signal from BEFWM recovers the original laser frequency by frequency-upshifting a Stokes-shifted probe beam, suitable for subsequent amplification in a chain of iodine laser amplifiers. The power conversion efficiency of 30% through BEFWM and the pulse compression from 50 ns to 3 ns between the incident laser and the output signal have been obtained.
Cavity Parameters of ZnCdSe/ZnSe Single-Quantum-Well Separate-Confinement-Heterostructure Laser Diodes
Authors: Tsujimura Ayumu , Yoshii Shigeo , Hayashi Shigeo , Kazuhiro Ohkawa Kazuhiro Ohkawa , Tsuneo Mitsuyu Tsuneo Mitsuyu
Published: February 2005

The cavity length dependence of the external differential quantum efficiency and the threshold current density was investigated for ZnCdSe/ZnSe single-quantum-well separate-confinement-heterostructure laser diodes at 77 K. An internal loss of 1.5 cm-1, an internal quantum efficiency of 61% for stimulated emission, a transparency current density of 1.8 kA/(cm2·µm) and a gain factor of 0.36 cm2·µm/A were obtained. The transparency current density is 3-4 times larger than that for bulk GaAs. Improvement in the internal quantum efficiency for spontaneous emission will lead to reduction of the operation current.
Highly Repetitive Picosecond Polarization Switching in Type-II AlGaAs/AlAs Multiple Quantum Well Structures
Authors: Kawazoe Tadashi , Tomobumi Mishina Tomobumi Mishina , Yasuaki Masumoto Yasuaki Masumoto
Published: February 2005

We have demonstrated highly repetitive picosecond polarization optical switching operation of type-II quantum well structures at room temperature. The switching mechanism is due to the fast Γ-X interlayer scattering of electrons and the fast spin relaxation of holes. According to our experimental results, the switching time is less than 1 ps, the switching power is as low as 3 nJ/cm2, and the switching repetition rate is more than 80 GHz. Moreover we point out the possibility of continuous optical switching operation for future applications.
Effect of Nonstoichiometry on Dielectric Properties of Strontium Titanate Thin Films Grown by ArF Excimer Laser Ablation
Authors: Hirano Takashi , Masahiro Taga Masahiro Taga , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

Dielectric properties and lattice parameters of nonstoichiometric strontium titanate were systematically investigated. The X-ray diffraction measurements indicated the formation of SrO·(SrTiO3)
n
(n=4-53) instead of SrTiO3 with excess Sr. Epitaxial films grown on (111)Pt/(100)MgO by an ArF excimer laser ablation method were mostly orientated along the (102n+1) axis. With decrease in the frequency of Sr-O plane sliding-in (increasing n value), the dielectric constant ε increased from 87ε0 to 300ε0. Furthermore, an improved property was also obtained in its temperature dependence. The sublattice (perovskite SrTiO3) in the vicinity of sliding-in Sr-O plane was slightly distorted (compressed by about 15%).
Step-Coverage Simulation for Molybdenum Silicide Sputtering Film
Authors: Yamazaki Toshinari , Ikeda Nagayasu , Nakashima Yoshiro , Sugimoto Keiro , Kitahara Akira
Published: February 2005

Step-coverage calculation for molybdenum silicide films was carried out using a model constructed by modifying the string model often used for the calculation of aluminum film step coverage. In the model, the film composition around steps as well as the thickness can be calculated. It was concluded that the difference between the angular distribution of the Mo atom and that of the Si atom caused not only the nonuniformity of the film composition at flat surface but also the deviation of the film composition around steps from that at flat surface.
Synthesis of Nanostructured Diamond via Controlled Surface Pretreatment in Hexane Medium
Authors: Okubo Tatsuya , Nakata Shinobu , Nagamoto Hidetoshi , Ihara Manabu , Komiyama Hiroshi
Published: February 2005

The grain density of chemical vapor deposition (CVD) diamond film is greatly enhanced via controlled surface pretreatment in hexane medium under ultrasonic irradiation. Surface treatment of the substrate prior to the deposition is essential for continuous diamond film formation by CVD processing. Generally the pretreatment is carried out using diamond powder dispersed in alcohol or acetone medium under ultrasonic irradiation. In this study we used hexane as a dispersion medium, and synthesized diamond on a silicon wafer by conventional microwave plasma-enhanced CVD (MPCVD). The grain size of a continuous film whose substrate is treated in hexane is successfully reduced to ∼100 nm. The corresponding grain density is enhanced to ∼1010/cm2. The diamond film is homogeneously blue in color. When the substrate is treated in acetone, the density is in the range of 108/cm2 under the same synthesis conditions.
On the Definition of Sequential Tunneling in a Double-Barrier Resonant Tunneling Structure
Authors: Yasuhito Zohta Yasuhito Zohta
Published: February 2005

It is pointed out that sequential tunneling has, until now, been defined in two ways in the literature, and this has led to some confusion. It is shown that sequential tunneling defined as a two-step process is an alternative description of resonant tunneling, but not an alternative mechanism for it.
The Selective Deposition of a Silicon Film on Hydrogenated Amorphous Silicon by Mercury Sensitized Photochemical Vapor Deposition
Authors: Hiramatsu Masato , Ishida Arichika , Takaaki Kamimura Takaaki Kamimura , Yoshito Kawakyu Yoshito Kawakyu
Published: February 2005

The authors have developed a low-temperature process for the first time for the selective deposition of a silicon film on hydrogenated amorphous silicon (a-Si:H) and on silicon nitride (SiN
x
) surfaces by mercury sensitized photochemical vapor deposition (Photo-CVD). The selective deposition of Si films was able to be achieved by hydrogen radical cleaning for 1 minute prior to the deposition. There were two different incubation periods for the a-Si:H and SiN
x
surfaces. Selective deposition was obtained by using this difference in the incubation periods between the deposition on an a-Si:H surface and on a SiN
x
surface. The field effect mobility and the off leakage current for thin film transistor (TFT) of the fabrication by using this selective deposition technique were of the 0.6 cm2 V-1 s-1 and 10-11 A order, respectively. It has been confirmed that photo-CVD is a promising method for the selective deposition process at a low temperature using a large-area glass substrate.
Surface Currents in InP/InGaAs Heterojunction Bipolar Transistors Produced by Passivation Film Formation
Authors: Fukano Hideki , Yoshifumi Takanashi Yoshifumi Takanashi , Masatomo Fujimoto Masatomo Fujimoto
Published: February 2005

The correlation between the passivation film formation for InP/InGaAs heterojunction bipolar transistors and transistor current-voltage (I-V) characteristics is investigated. The I-V characteristics vary significantly depending on the kind of passivation films. The major change in I-V characteristics is the increase in base current (I
b),which implies the generation of an additional recombination process around the surface of the emitter-base junction. A change in collector current (I
c) is also observed, indicating that the electron injection mechanism changed near the passivated semiconductor surface. These surface currents are produced by the interaction of the semiconductor surface with the passivation films. It is shown that these surface currents are greatly suppressed using a buffered hydrofluoric acid solution before the passivation film formation.
Dimensional Crossover Effect of Pinning in YBa2Cu3O7 Films
Authors: Awaji Satoshi , Watanabe Kazuo , Kobayashi Norio , Hisanori Yamane Hisanori Yamane , Toshio Hirai Toshio Hirai
Published: February 2005

Temperature and field dependence of the critical current density J
c and its anisotropy in chemical vapor deposition processed (CVD) YBa2Cu3O7 films deposited on SrTiO3(100) substrates were measured by a 4-probe resistive method. A kink in the temperature dependence of J
c was found for B⊥c, while there was no kink in J
c for B//c. This kink can be explained as the dimensional crossover effect from three-dimensional (3D) pinning to two-dimensional (2D) pinning. Below the temperature at which the kink appears, the 2D pinning affects the J
c properties. The pinning model for 3D and 2D cases is explored, considering the extrinsic pinning and the intrinsic one, respectively.
Grain Size Control of Bi-Substituted Garnet Films Crystallized by Multi-Step Rapid Thermal Annealing for Magneto-Optical Disks
Authors: Kim Hyeon Soo , Yong Hee Lee Yong Hee Lee , Sang Soo Lee Sang Soo Lee
Published: February 2005

The sputtered Bi-substituted iron garnet films of improved microstructures are successfully grown using the optimized multi-step rapid thermal annealing (MSRTA). The concepts of the incubation time and the relaxation time in the MSRTA are applied to obtain good microstructures of garnet films. By repeating the optimized thermal cycle many times, the high density of nucleated grains can be obtained, and the grain size can be forced to be as small as it can be. This optimized MSRTA leads to a finer grain size of less than 0.1 µm and better surface morphology with higher grain density than a conventional annealing method. The crystallized sample shows good squareness and large remnant Faraday rotation.
Rate Equation Analysis of a Pulsed Microcavity Laser
Authors: Ujihara Kikuo , Michihiro Osuge Michihiro Osuge , Munehiro Takaku Munehiro Takaku
Published: February 2005

On the basis of rate equations it is shown that a microcavity laser can exhibit a distinct threshold in a pulsed operation even if the laser cavity has a large spontaneous emission coupling ratio.
Fabrication of GaAs Quantum Wire Structures by Hydrogen-Assisted Molecular Beam Epitaxy
Authors: Sugaya Takeyoshi , Kaneko Makoto , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

GaAs Quantum wire structures have been fabricated by hydrogen-assisted molecular beam epitaxy on substrates having V-shaped grooves, the side walls of which consist of (111)A. The growth rate of GaAs on (111)A was significantly decreased by atomic hydrogen irradiation, while that on (001) was increased. The large difference in the growth rate between (001) and (111)A has been uniquely utilized for the fabrication of quantum wires. The existence of a quantum energy level in the quantum wire structures has been confirmed by photoluminescence (PL) measurement. The PL spectra showed a clear polarization dependence.
Heterodyne Force-Detection for High Frequency Local Dielectric Spectroscopy by Scanning Maxwell Stress Microscopy
Authors: Yokoyama Hiroshi , Mark J. Jeffery Mark J. Jeffery , Takahito Inoue Takahito Inoue
Published: February 2005

The scanning Maxwell stress microscope (SMM) is a type of non-contact scanning force microscope, capable of imaging a variety of electrical and topographical features of surfaces solely based on harmonic analysis of the electric field-induced oscillations of the cantilever. We propose here a heterodyne force-detection scheme which enables the SMM to perform local dielectric spectroscopy up to high frequencies beyond the mechanical resonance of the cantilever. The method exploits the nonlinear dependence of the Maxwell stress on the field strength, which acts as a mechanical frequency mixer to create a low frequency beat force on the tip from closely separated high frequency electric-field components. The amplitude and the phase of the beat force carry information on the dielectric constant and loss at the high frequencies.
New Layered Vanadium Oxide with Negative Magnetization, Sr4V3O8-δ
Authors: Fukushima Noburu , Takeno Shiro , Shigenori Tanaka Shigenori Tanaka , Ken Ando Ken Ando
Published: February 2005

A new layered perovskite vanadium oxide Sr4V3O8-δ was synthesized and its crystal structure and magnetic properties were studied. Sr4V3O8-δ has a novel crystal structure, containing a V-O octahedron and a two-fold V-O fence in a unit cell. It exhibits negative magnetization below 30 K, when cooled in a magnetic field. This magnetism was explained based upon a N-type parasitic ferrimagnetism model.
Influence of Grain Boundary Configuration in Aluminum Films on Abrupt Resistance Changes during Electromigration
Authors: Hong Chao-Fu , Togo Mitsuhiro , Hoh Koichiro
Published: February 2005

Resistance changes accompanying electromigration were measured in aluminum thin-film interconnections with three different types of grain boundary (GB) configuration. Abrupt and oscillatory changes in resistance were observed and they were related to the number of grain-boundary triple points (GBTPs) in the sample and the connections between them by grain boundaries. This result supports the model that abrupt resistance change occurs when an aggregate of vacancies with considerable size makes a transition to the void at a certain GBTP.
Rotational Motion of Inorganic Diamagnetic Crystals Induced in the Magnetic Field
Authors: Chiaki Uyeda Chiaki Uyeda
Published: February 2005

The rotational motion due to diamagnetic anisotropy was first reported for large single crystals of quartz and corundum, in the magnetic field where the restoring force of the suspending string became negligible. The suspended crystal rotated gradually with the increasing field, and the diamagnetic principal axis was oriented in the direction parallel to the field. Harmonic oscillations were observed for the crystals in high magnetic field, and the period of oscillation was proportional to the reciprocal of the field. The precise value of diamagnetic anisotropy was obtained from the period of oscillation, and was estimated to be 5.45×10-9 emu/cm3 for quartz and 4.19×10-9 emu/cm3 for corundum.
Effect of Ambient Oxygen Gas on the Transport of Particles Produced by Laser Ablated YBa2Cu3O7-x
Authors: Kumuduni Wanniarachchi K. A. , Nakayama Yasushi , Nakata Yoshiki , Tatsuo Okada Tatsuo Okada , Mitsuo Maeda Mitsuo Maeda
Published: February 2005

The time-of-flight (TOF) distributions of particles produced by an ArF laser-ablated YBa2Cu3O7-x
were measured by laser-induced fluorescence spectroscopy (LIF) under different ambient oxygen gas pressures. Nascent Y atoms react with oxygen during their flight and form YO. Transport of particles through the ambient oxygen gas is well described by the drag model at low pressures and by the shock model at high pressures. It has been found in our present experiment that the critical pressure at which the transition occurs from the drag to the shock propagation is around 100 mTorr.
Lateral P-N Subband Junctions Fabricated on Patterned Substrates
Authors: Yamamoto Teiji , Inai Makoto , Toshihiko Takebe Toshihiko Takebe , Toshihide Watanabe Toshihide Watanabe
Published: February 2005

Lateral p-n subband junctions (LSJ) have been proposed that combine vertical quantum confinements with lateral p-n junctions using an amphoteric dopant Si and patterned substrates. The LSJ was fabricated at the interface between the flat and on the sloped surfaces of Si-delta-doped quantum structures grown on the patterned (111)A substrates. When the forward currents are injected into the LSJ, a recombination emission with a higher level of energy than in the bulk GaAs can be observed. Moreover, we have found tunneling phenomena with negative differential resistance in the LSJ. It was also demonstrated that LSJ structures have a high potential for applications in optic and electrical devices.
LaC2 Encapsulated in Graphite Nano-Particle
Authors: Tomita Masato , Saito Yahachi , Takayoshi Hayashi Takayoshi Hayashi
Published: February 2005

Arc discharging carbon rods containing 8.8 wt% La2O3 produces a carbonaceous deposit containing nano-particles (nm-size particles) consisting of graphite shells around core nano-crystals averaging 10-30 nm in diameter but sometimes 3-4 nm. Transmission electron microscopy, nm-size electron diffraction and electron energy-loss spectroscopy have revealed that the nano-crystals are La-carbide, LaC2, that the interfaces between the carbide and the graphite are flat, and that no intermediate layers are formed.
Influence of Sputtering Geometry on Crystallinity of Al(110) Thin Films on Offset (100)Si
Authors: Yokoyama Shin , Hiroshi Ichikawa Hiroshi Ichikawa , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: February 2005

The quality of Al(110) deposited by means of dc magnetron sputtering on misoriented (100) Si has been examined for various incident geometries between the Al beam and the vicinal Si surface. The ideal atomic step configuration of this substrate is similar to a stairway. Three directions of incidence (downstairs, upstairs and from the side of the stairway) were investigated. The X-ray diffraction measurements indicate that the crystallinity is improved for the upstairs grazing incidence. The results are explained in terms of the enhanced Al surface migration due to the grazing incidence and the dominant growth at the steps on the surface.
Low Temperature Surface Cleaning of InP by Irradiation of Atomic Hydrogen
Authors: Chun Yong Jin , Sugaya Takeyoshi , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

The effects of atomic hydrogen irradiation on the surface cleaning of InP substrates have been investigated by reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES). Carbon and oxygen-free clean surfaces of InP have been produced for a temperature range of as low as about 350°C for 30 min irradiation of atomic hydrogen. Under this condition, the RHEED patterns have revealed phosphorus-stabilized (2×4) reconstructed surfaces while indium-stabilized (4×2) reconstruction patterns have been observed upon cleaning by using the conventional arsenic irradiation at 530°C.
High Performance Double Delta Doping GaAs/In0.25Ga0.75As/GaAs Pseudomorphic Heterostructure
Authors: Shieh H. M. , Hsu W. C. , C. L. Wu C. L. Wu , T. S. Wu T. S. Wu
Published: February 2005

We report the preparation of high two-dimensional electron gas (2DEG) concentration and mobility in double delta doping, single quantum well GaAs/In0.25Ga0.75As/GaAs pseudomorphic heterostructure by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Superior in gate voltage swing (3 V), saturation current density, and extrinsic transconductance to those of conventional In
x
Ga1-x
As/GaAs pseudomorphic heterostructures with similar gate length (2 µm) ever reported, were achieved.
High Current Gain AlGaAs/GaAs Heterojunction Bipolar Transistors with Carbon-Doped Base Grown by Gas Source Molecular Beam Epitaxy Using Trimethylamine Alane as the Aluminum Source
Authors: Yamaura Shinji , Ando Hideyasu , Okamoto Naoya , Sandhu Adarsh , Takahashi Tsuyoshi , Toshio Fujii Toshio Fujii , Naoki Yokoyama Naoki Yokoyama
Published: February 2005

We report on AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with a 70 nm-wide 3.4×1019 cm-3 carbon-doped base, grown by gas-source molecular beam epitaxy (GSMBE) using trimethylamine alane (TMAAl) as the aluminum source. We reduced the residual carbon concentration of the AlGaAs emitter layer to less than the secondary ion mass spectroscopy (SIMS) detection limit (1×1016 cm-3) by optimizing the overall growth conditions. The DC current gain of 160, obtained at a current density of 3×104 A/cm2, is the highest value ever reported for GSMBE-grown AlGaAs/GaAs HBTs.
Study of Ba1-xKxBiO3 Superconducting Crystals Grown by Anodic Electrocrystallization Method
Authors: Tang Horng-Yi , Chen Wen-Lin , Chien Ting-Ray , Norton Michael L. , Maw-Kuen Wu Maw-Kuen Wu
Published: February 2005

Crystalline bismuthates Ba1-x
K
x
BiO3 with x greater than 0.5 are obtained by a low temperature anodic electrocrystallization method in a potassium hydroxide molten flux. The x=0.56 bismuthate crystal shows 8 K superconductivity determined by SQUID measurement. Transport measurements on these crystals show that the temperature dependence of the normal state resistivity follows a simple power law up to the second order, while the Hall coefficient is temperature independent.
Antiphase Dynamics in a Modulated Multimode Laser
Authors: Otsuka Kenju , Mandel Paul , Georgiou M. , Etrich C.
Published: February 2005

Antiphase periodic oscillations and clustering in a modulated microchip multimode solid-state laser have been demonstrated experimentally. Chaotic relaxation oscillations featuring intermode statistical non-independence that result from cross-saturation dynamics among oscillating modes have been observed.
Cd-Doped InGaN Films Grown on GaN Films
Authors: Nakamura Shuji , Naruhito Iwasa Naruhito Iwasa , Shin-ichi Nagahama Shin-ichi Nagahama
Published: February 2005

Cd-doped InGaN films were grown for the first time at temperatures between 810°C and 780°C. Room-temperature photoluminescence (PL) showed strong blue emissions which had peak wavelengths between 424 nm and 495 nm, depending on the indium mole fraction, and full width at half-maximum (FWHM) of about 60 nm. These blue emissions had a peak wavelength at an energy level 0.5 eV lower than the band-gap energy of each InGaN. The intensity of the Cd-related emission was almost the same as that of the band-edge (BE) emission of Si-doped InGaN.
Real-Time Synchrotron Phase Detection by the Electro-Optical Measurement of Synchrotron Radiation
Authors: Atsushi Ogata Atsushi Ogata
Published: February 2005

A method to measure the phases of synchrotron oscillation in a storage ring is proposed. It utilizes Pockels cells, which modulate the amplitudes of synchrotron radiation signals by two sinusoidal electric signals with inverse phases and send them to two optical-to-electric converters. A differential amplifier produces a difference in the resultant signals, which is proportional to the synchrotron phase over a certain range. Although the results depend on the bunch current, a similar electrooptic technique can be used to correct them.
Spatial Distribution and Surface Loss of CF3 and CF2 Radicals in a CF4 Etching Plasma
Authors: Hikosaka Yukinobu , Hirotaka Toyoda Hirotaka Toyoda , Hideo Sugai Hideo Sugai
Published: February 2005

The absolute number density and the spatial distribution of CF3 and CF2 radicals in a radio-frequency CF4 plasma were measured using threshold-ionization mass spectrometry. The time constant of density decay in an afterglow was measured to be almost independent of pressures (15-100 mTorr) and rf powers (10-100 W). This suggests that surface reactions rather than gas phase reactions may primarily be responsibile for the radical loss. The surface loss probability s of CF3 and CF2 radicals was estimated in this well-defined system to be s=0.012 and 0.014, respectively.
Formation of Two-Dimensional Electron Gas in N-AlGaAs/GaAs Heterojunctions on (111)B Microfacets Grown by Molecular Beam Epitaxy on a Patterned (001) Substrate
Authors: Nakamura Yusui , Tsuchiya Masahiro , Koshiba Shyun , Noge Hiroshi , Hiroyuki Kano Hiroyuki Kano , Hiroyuki Sakaki Hiroyuki Sakaki
Published: February 2005

Selectively doped N-AlGaAs/GaAs heterojunctions have been successfully prepared by molecular beam epitaxy (MBE) in 1-µm-wide (111)B microfacets formed on mesa-patterned (001) substrates. The sample exhibited a clear Shubnikov de Haas oscillation that was dominated by the magnetic field component perpendicular to the (111)B facet, and gave clear evidence of the formation of the two-dimensional electron gas in (111)B facets. The sheet electron density and electron mobility were estimated to be 3×1011 cm-2 and more than 8000 cm-2·V-1·s-1, respectively. These results indicate the possibility of forming edge quantum wires and other microstructures of very small cross-sectional dimensions on MBE grown facet structures.
Noncontact Characterization for Carrier Recombination Center Related to Si-SiO2 Interface
Authors: Ken-ichi Katayama Ken-ichi Katayama , Fumio Shimura Fumio Shimura
Published: February 2005

The energy levels of carrier recombination centers originating from an Si-SiO2 interface were investigated for the first time by means of a noncontact and nondestructive laser/microwave photoconductance technique. An energy level of the carrier recombination center around 0.2 eV, which can be attributed to a trivalent silicon defect, i.e., the P
b0 center, was obtained from the temperature dependence of the Shockley-Read-Hall lifetime for (100) silicon wafers with native or thermal oxide.
Anomalous Biophoton Emission during Germination Process of Red Bean
Authors: Kai Shoichi , Tomohiko Mitani Tomohiko Mitani , Masahiro Fujikawa Masahiro Fujikawa
Published: February 2005

Spontaneous biophoton emission was investigated for the germination and the growth process of a red bean seed. The growth process of the root of a red bean after germination was statistically investigated for a total of 2000 seeds whose average root growth dynamics was well described by a simple logistic equation. Strong biophoton emission was observed at two inflection points of the logistic curve. Namely, when maximum acceleration of the root growth occurred, maximum biophoton emission was observed.
Formation of Carbon Nitride Films by Means of Ion Assisted Dynamic Mixing (IVD) Method
Authors: Ogata Fuminori Fujimoto
Published: February 2005

Nitrogen-rich films of carbon nitride were prepared for the first time on silicon wafers and tungsten carbide plates by means of the ion-assisted dynamic mixing (or ion and vapor deposition, IVD) method. The thickness of the films was 1.0 µm and the composition ratio, C/N, was changed from 0.2 to 2.0. The energy of nitrogen ions also varied from 200 eV to 20 keV. The structure of films was amorphous. The Knoop hardness of films grown on WC was about 6500 for the films with atomic ratio of composition lower than C/N=1.0 and prepared by means of 200 and 500 eV beams. This hardness of the present films with 1.0 µm thickness is never obtained in films of other materials. The X-ray photoelectron spectroscopy spectra of C-1s 1/2 electrons from these films showed a larger chemical shift (286.3 eV) than that of diamond (285.8 eV), which was observed for the first time.
Single-Crystal Structural Study of fcc and hcp C60 from 107 to 298 K Using Synchrotron X-Rays
Authors: Kitamoto Tatsuya , Sasaki Satoshi , Atake Tooru , Tanaka Toshiaki , Kawaji Hitoshi , Kikuchi Koichi , Saito Kazuya , Suzuki Sinzo , Achiba Yohji , Ikemoto Isao
Published: February 2005

The crystal structure of pure C60 has been determined by means of single-crystal diffraction methods using synchrotron X-rays at room and below room temperatures. Both fcc and hcp single crystals were found in one-run product by means of the precession method and a four-circle diffractometer. The fcc phase at 266 K gave the best fit for a shell model with the fullerene radius r=3.52 Å. The radius did not change significantly at lower temperatures but deviation from the free rotation model was detected for smaller B
iso and larger R values. The least-squares calculation for the hcp phase converged at (1/3, 2/3, 0.459) for the one-sided fullerene, suggesting that solvent residue may remain in the crystal.
Photoluminescence and Photoemission Studies of Defects in InP Induced by Zn Diffusion
Authors: Morio Wada Morio Wada , Katsutoshi Sakakibara Katsutoshi Sakakibara
Published: February 2005

Defects in InP induced by Zn diffusion have been studied by measuring the photoluminescence and photoemission spectra in Zn-diffused samples fabricated using our new diffusion technique. Results indicate that Zn diffusion generated broad emission bands in the energy range of 0.7-1 eV only in the surface layer with a thickness of less than about 100 nm and left a P-rich layer with a very high Zn concentration and a thickness of less than about 20 nm. It is suggested that Zn diffusion with a high Zn-concentration source under P-rich conditions occurs near the surface and induces deep centers responsible for these bands.
(Nb, Ti)3Sn Superconducting Magnet Operated at 11 K in Vacuum Using High-Tc (Bi, Pb)2Sr2Ca2Cu3O10 Current Leads
Authors: Watanabe Kazuo , Yamada Yutaka , Sakuraba Junji , Hata Fumiaki , Chong Chin Kung , Hasebe Tsuginori , Ishihara Mamoru
Published: February 2005

A conduction-cooled superconducting magnet using high-T
c oxide current leads was successfully demonstrated. We succeeded in constructing the (Nb, Ti)3Sn multifilamentary superconducting magnet system without liquid helium, which is operated at 11 K in vacuum using a cryocooler and generates a magnetic field of 4.6 T in a 50 mm bore (38 mm room temperature bore). Use of (Bi, Pb)2Sr2Ca2Cu3O10 current leads effectively contributed to realization of the compact cryostat with large current leads of 500 A.
Theoretical Studies of the X-Ray Mirror Surface Roughness
Authors: Tong Xiao-Min , Yamaoka Hitoshi , Tomoya Uruga Tomoya Uruga , Etsuo Arakawa Etsuo Arakawa
Published: February 2005

Theoretical studies on the X-ray mirror surface roughness are presented. The relations of scattered and reflected X-ray intensities from rough surface with incident beam intensity are formulated. Based on the formula, numerical fitting method is used to derive the mirror surface roughness σ and mirror surface mean slope β as well as the power spectrum ω(p) from the X-ray scattering experiments. Compariosn with other experimental data is also discussed.
Organic Electroluminescent Devices with 8-Hydroxyquinoline Derivative-Metal Complexes as an Emitter
Authors: Hamada Yuji , Sano Takeshi , Fujita Masayuki , Fujii Takanori , Yoshitaka Nishio Yoshitaka Nishio , Kenichi Shibata Kenichi Shibata
Published: February 2005

Organic electroluminescent (EL) devices with 8-hydroxy-quinoline derivative-metal complexes (Znq2, Beq2, Mgq2, ZnMq2, BeMq2 and AlPrq3) as the emitter have been developed. The emissions of these devices are green or yellow. These devices have a luminance of more than 3000 cd/m2. In particular, the EL device with Znq2 has a luminance of 16200 cd/m2.
Optical Absorption of Co2+ in CuAlS2
Authors: Aksenov Igor , Kai Tetsuya , Nobuyuki Nishikawa Nobuyuki Nishikawa , Katsuaki Sato Katsuaki Sato
Published: February 2005

The optical absorption spectra of CuAlS2:Co were studied at RT and 70 K in near IR and visible regions. The spectra exhibit two fine structured bands around 1450 nm and 750 nm, as well as a large red shift of the absorption edge of CuAlS2, which has been assumed to occur due to Co3+→Co2+ charge transfer type transitions. The fine structures are attributed to the transitions in the 3d-shell originated orbitals of Co2+ ion, and are analyzed in the framework of the crystal field theory in the first approximation.
Multistable Charge Build-Up and a New Switching Principle in Coherent-Electron Tunneling Devices
Authors: Mathias Wagner Mathias Wagner , Hiroshi Mizuta Hiroshi Mizuta
Published: February 2005

A new mechanism leading to multiple stable operating states in coherent-electron tunneling devices is proposed and numerically verified in a model system. This mechanism utilizes the charge accumulation in virtually bound and quasi-bound states in a quantum-well/barrier structure. The electrostatic energy associated with these states causes the lowest occupied of them to be pinned to the conduction-band edge. For fixed bias, more than one solution to the Poisson equation is found, with each solution being uniquely determined by the quantum number of the pinned state. These different solutions show up as different current branches in the I(V) characteristic of a tunneling diode. Switching between them – for example by using lateral gates – should be very fast, as virtually bound states have a much shorter life time than quasi-bound states.
Iodine Doping in ZnSe in High-Temperature Range by Metalorganic Vapor-Phase Epitaxy
Authors: Fujimoto Masahiro , Suemune Ikuo , Hirofumi Osaka Hirofumi Osaka , Yoshihisa Fujii Yoshihisa Fujii
Published: February 2005

Iodine doping in ZnSe was studied by means of atmospheric-pressure (AP) metalorganic vapor-phase epitaxy (MOVPE). Electron concentration greater than 1×1018 cm-3 was observed for growth temperatures above 500°C, and the photoluminescence from the doped ZnSe films was dominated by the neutral-donor bound exciton line. The growth temperature dependence curve of the electron concentration in the doped films was gentle up to the growth temperature of 580°C, in contrast to the sharp decrease in electron concentrations above the growth temperature of 400°C in low-pressure (LP) MOVPE. The main factor that gives the great difference in the doping properties between AP- and LP-MOVPE is discussed from the viewpoint of the working pressure.
Ordering of Missing-Row-Defects Forming (2×n)-Bi Phases on the Si(100) 2×1 Surface Studied by the Scanning Tunneling Microscopy
Authors: Park Chan , Bakhtizin Raoulf Z. , Tomihiro Hashizume Tomihiro Hashizume , Toshio Sakurai Toshio Sakurai
Published: February 2005

(2×n)-Bi phases formed on the Si(100) 2×1 surface are studied by LEED and scanning tunneling microscopy. A series of well ordered (2×n) superlattices, with n ranging from 5 to 12, are observed. The STM images show that the (2×n) structures result from the formation of the periodic arrays of the missing Bi-dimer rows. The n of the (2×n) structure is found to depend on the Bi coverage θ with a relationship of θ=1-1/n. However, for the phases with n smaller than 5, the ordering of missing rows in the “n” direction is found to be disturbed by the competing formation of rectangular and linear type defects. The formation of successive (2×n) phases as a function of coverage suggests the presence of strong long range repulsive elastic interactions among missing Bi-dimer rows.