bluuebunny/crossref_metadata_2025 huggingface dataset:
Noise Enhancement of Period Doubling in Strongly Modulated Semiconductor Lasers
Authors: Kao Yao Huang , Wang Hung Tser Lin
Published: February 2005

In this paper the phenomena of period doubling and bistability of multiple spiking states in deeply modulated laser diodes are investigated. The situations of in which the period doubling in the parameter space occurs are indicated. The influence of noise on the period doubling is examined by employing the singl-mode rate equations with Langevin noise.
Photocurrent in Thin YBa2Cu3O6 Films on Sapphire
Authors: Ullrich Bruno , Kula\cc Ibrahim , Pint Harald , Günther Leising Günther Leising , Hartmut Kahlert Hartmut Kahlert
Published: February 2005

Photocurrents in thin YBa2Cu3O6 films were measured at 300 K and 77 K. It is demonstrated that the classical semiconductor theory holds for this kind of material. The photocurrent results are discussed and compared with luminescence and optical transmission measurements. A large energy shift (0.63 eV), to date not observed in other semiconductors, between the photocurrent and luminescence maxima was measured. An oxygen surplus in the bulk of the sample is assumed to be the reason. Furthermore, it is demonstrated that at the critical temperature (T
c=93 K) of superconductive YBa2Cu3O7 a change in the dark conductance behavior of semiconducting YBa2Cu3O6 takes place.
Strong Wavelength Dependence of Laser Ablation Fragments of Superconductor YBa2Cu3Oy
Authors: Eryu Osamu , Murakami Kouichi , Masuda Kohzoh , Shihoyama Kazuhiko , Mochizuki Takayasu
Published: February 2005

In addition to the two groups of radiative fragments which have previously been described, two groups of nonradiative fragments are first observed in laser-ablated fragments of YBa2Cu3O
y
, using a space/time-resolved optical transmittance measurement. The average velocities of the nonradiative fragments (2×105 cm/s and 2×104 cm/s) are much lower than those of the radiative fragments (5×106 cm/s and 1×106 cm/s). The yield of the nonradiative fragments increases with increasing laser wavelength, while that of the radiative fragments is nearly wavelength independent.
Grating-Coupled Light Emission from the Slow Mode of Metal-Insulator-Metal Tunnel Junctions
Authors: Ushioda Sukekatsu , Uehara Yoichi , Takada Masatoshi , Koji Otsubo Koji Otsubo , Junichi Murota Junichi Murota
Published: February 2005

We have observed the direct light emission from the slow mode of surface plasmon polaritons (SPP) of metal-insulator-metal (MIM) tunnel junctions formed on a ultra-fine grating. The grating (period=100 nm, groove depth=12 nm, area=200 µm×200 µm) was created on a Si(100) wafer, using a direct electron beam lithography technique and wet etching of SiO2 The MIM junction was formed by evaporation of Al and Au films on this grating. The emission peak for the Al-Oxide-Au junction was observed at 1.55 eV that is expected from the dispersion curve of the slow mode. The spectral width is appreciably narrower than the emission due to the natural residual micro-roughness of the junction.
Field Ion-Scanning Tunneling Microscopy Study of Sulfur/Chlorine Adsorption on the Cu(111) 1×1 Surface
Authors: Motai Kumi , Hashizume Tomihiro , Jeon Dong-Ryul , Lu Hua , Tanaka Ken-ichi , Pickering Howard W. , Toshio Sakurai Toshio Sakurai
Published: February 2005

Adsorption of sulfur and chlorine was studied on the Cu(111)1×1 surface using a field ion-scanning tunneling microscope. Atomically resolved high-quality STM images were obtained for the first time.
A Plane Wave Diffraction on an Amplitude-Phase Laue Microinterferometer
Authors: Snigirev A. A. , Suvorov A. Yu. , Ishikawa Tetsuya , Izumi Koichi , Kikuta Seishi
Published: February 2005

X-ray diffraction images formed by an incident beam with spatial inhomogeneity in Laue geometry are presented. A gold mask with a period of 40 µm and a strip thickness of 1.2 µm was used to modulate the incident monochromatic plane wavefront. Numerical simulations of the obtained images were produced and comparative analysis was carried out from the viewpoint of classical optics.
Simultaneous Observation of 3-Dimensional Magnetic Stray Field and Surface Structure Using New Force Microscope
Authors: Hosaka Sumio , Kikukawa Atsushi , Honda Yukio , Hajime Koyanagi Hajime Koyanagi , Shinji Tanaka Shinji Tanaka
Published: February 2005

A 3-dimensional (3-D) magnetic stray field and the surface structure have been observed using an atomic and magnetic force microscope (A/MFM) with an optical-beam-deflection force detector. Measurement is carried out by operating the microscope as a surface structure observer in constant repulsive force AFM mode. The 3-D magnetic stray field measurement is done in force gradient MFM mode with probe position control above the surface. Initial results have demonstrated that the 3-D magnetic stray field and surface structure of magneto-optical disk can be imaged simultaneously.
Observation of Soft X-Ray Amplified Spontaneous Emission in a Recombining Si Plasma Pumped by a Low-Power Laser
Authors: Yashiro Hidehiko , Hara Tamio , Ando Kozo , Negishi Fumiko , Ido Syunji , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: February 2005

Amplified spontaneous emissions of Li-like ions were observed in a recombining Si plasma which was produced by a Nd-glass laser of table-top size. The small signal gain coefficient of Si XII 3d-5f (88.84 Å) was evaluated at 0.9 cm-1, and the emissions of Si XII 3d-4f (130.02 Å) and 3p-5d (87.36 Å) transitions show small amplifications. The driver laser pulse has a time envelope of 4 ns-FWHM (full width at half maximum) and contains several short pulses of about 120 ps-FWHM with time intervals of about 350 ps. The average irradiation power density of a short pulse was estimated to be only 5×1011 W/cm2.
A Theoretical Investigation of the Metastability of Epitaxial α-Sn on a (100) Zinc Blende Substrate
Authors: Tomonori Ito Tomonori Ito
Published: February 2005

The metastability of α-Sn with a diamond structure on a (100) zinc blende substrate is discussed based on cohesive energy calculations for bulk form and thin layers using the pseudopotential perturbation approach and universal empirical potentials. In the bulk form, α-Sn is found to be more stable than β-Sn with double-bct structure by 50 meV/atom at 0 K. However, the β-Sn is stabilized by the contribution of vibration entropy at high temperatures. The stabilization of α-Sn on the (100) zinc blende substrate is due to small coordination number change at the interface between thin films and substrate. On the zinc blende CdTe substrate, α-Sn is more stable than β-Sn by 291 meV/atom at the interface region and 628 meV/atom at the thin films region.
Titanium/Gold Schottky Contacts on P-Type GaAs Grown on (111)A and (100) GaAs Substrates Using Molecular Beam Epitaxy
Authors: Lovell David R. , Yamamoto Teiji , Inai Makoto , Toshihiko Takebe Toshihiko Takebe , Kikuo Kobayashi Kikuo Kobayashi
Published: February 2005

The Schottky barrier heights of Ti/Au contacts on p-type GaAs, grown on (111)A and (100) GaAs substrates by molecular beam epitaxy, have been investigated by I-V and C-V techniques. Higher barrier heights are observed for contacts on (111)A GaAs films. Comparison between our results and the ideal Schottky barrier height for Ti on p-type GaAs shows that Ti/Au barrier heights on p-type (111)A GaAs films are closer to the ideal case than the Ti/Au barrier heights on p-type (100) GaAs films. This suggests that the defect densities of the Ti-GaAs interfaces of Ti/Au contacts on (111)A GaAs films are lower than those of identical Ti/Au contacts on (100) GaAs films.
The Superconducting Properties of [001] Twist Boundaries in a Bi-Sr-Ca-Cu-O Superconductor
Authors: Tomita Naruaki , Takahashi Yutaka , Minoru Mori Minoru Mori , Yoichi Ishida Yoichi Ishida
Published: February 2005

Critical temperature (T
c) and critical current density (J
c) of [001]-twist bicrystals of the Bi2Sr2CaCu2O
x
were measured as a function of twist angle. The resistivity-temperature curve of the bicrystal showed a long tail, which was enhanced as the applied current increased. The J
c values of the bicrystals are 3-4 orders of magnitude lower than that of single crystals but relatively high J
c values were obtained for bicrystals at Σ5 and Σ17 coincidence orientation relationships. It was indicated that the [001] twist boundary in Bi2Sr2CaCu2O
x
was the weak link, and is suggested that there existed a less detrimental grain orientation.
Selectively Aligned Polymer Film Growth on Obliquely Evaporated SiO2 Pattern by Chemical Vapor Deposition
Authors: Yoshimura Tetsuzo , Motoyoshi Katsusada , Tatsuura Satoshi , Sotoyama Wataru , Azuma Matsuura Azuma Matsuura , Tomoaki Hayano Tomoaki Hayano
Published: February 2005

Polyazomethin films were grown by chemical vapor deposition using terephthalaldehyde and p-phenylenediamine gases on SiO2 film patterned in a 10-µm-wide stripe. When the SiO2 film was obliquely evaporated on a quartz substrate by tilting the substrate along the y-axis, while polymer chain alignment was random on the quartz, the chain on the SiO2 film aligned along the y-axis, which induced birefringence and dichroism selectively on the stripe pattern. When the SiO2 stripe was formed on a SiO2 film deposited by tilting the substrate along the x-axis, the chain direction in the stripe region was at right angles to that in the surrounding region.
Comparing Effects of Vacuum Annealing and Dry Oxidationon the Photoluminescence of Porous Si
Authors: Masao Yamada Masao Yamada , Kazuaki Kondo Kazuaki Kondo
Published: February 2005

Effects of vacuum annealing and dry oxidation on the photoluminescence properties of porous Si are reported. Anodized porous Si is formed by electrochemical etching in an aqueous HF solution of 16 to 48 wt% with a current density of 10 to 70 mA/cm2. A subsequent vacuum annealing (from 400°C to 800°C) weakens the intensity of the photoluminescence, whereas, oxidation using dry oxygen at 5 Torr above 800°C increases the intensity remarkably in addition to providing blue shifts as large as 100 nm. This study suggests that the visible photoluminescence is due to the modified quasi-direct band-gap structure of Si by the quantum confinement of electrons and holes.
A Numerical Design Study of Auto-Convergent Electron Gun for Color Cathode Ray Tube
Authors: Shuhei Nakata Shuhei Nakata
Published: February 2005

An auto-convergent electron beam gun system for a cathode ray tube (CRT) is proposed, designed and numerically simulated. The system can resolve the beam distortion caused by an aberration of symmetric electrostatic lenses and a higher order field of the deflection yoke, and produce a small beam spot diameter and convergence on the screen. The system consists of two kinds of lenses. One kind consists of three pre-forming lenses for the three beams and the other kind involves the assemblage of two quadrupole lenses, which are common to all beams. After the optimization of the shape of the electrodes and applied voltage on the electrodes, the performance of the lens system is verified by a ray tracing of the electron beams. From the calculation, the spot diameters of 0.3 mm×0.45 mm for the central beam and 0.4 mm×0.45 mm for the outer beam on the screen center are obtained.
Dependency of Adhesion Behavior on Thermal Stress Distribution in Photoresist Micropatterns
Authors: Kawai Akira , Takata Hitoshi Nagata
Published: February 2005

We report an excellent correlation between adhesive behavior in HF aqueous solution and internal distribution of thermal stress in a photoresist pattern. The stress distribution was analyzed using the two-dimensional finite element modeling in the cross section of the photoresist pattern. The large envelope shape, which indicates weak adhesion, was confirmed by the concentration of stress at the resist-substrate interface. In particular, the hardened layer of the photoresist pattern surface has the effect of forming the two-step shape of the etching envelope due to isotropic and lateral intrusion.
Measurement of Vapor Distribution in Gas Evaporation without Convection by Atomic Absorption Method
Authors: Sawai Shinya , Dohi Minoru , Kato Manabu , Nobuhiko Wada Nobuhiko Wada
Published: February 2005

Measurement of the distribution of zinc vapor atoms is carried out by means of atomic light absorption spectroscopy in the top-heating gas evaporation furnace which is developed for the gas evaporation without convection on the ground. Distribution of supersaturated vapor atoms in the wide range from the evaporating surface in the gas atmosphere is measured. The sizes and number densities of collected particles at various places on the collecting rod are interpreted in terms of measured vapor densities and temperatures at respective places.
A Positron Lifetime Study of Defects in Neutron-Irradiated Si
Authors: Li Anli , Huang Hanchen , Li Donghong , Zheng Shengnan , Du Hongshan , Iwata Shengyun Zhu
Published: February 2005

Positron lifetime measurements in neutron-irradiated Cz silicon crystals have been performed at room temperature after annealing at different temperatures between 100°C and 800°C. Two-component fitting of the positron lifetime spectra was carried out. It is suggested that the short lifetime component is a weighted average lifetime of the positrons in the bulk and those trapped at monovacancy-substitutional oxygen complexes, while the long lifetime component is an average lifetime of the positrons trapped at divacancies or divacancy-substitutional oxygen complexes and those trapped at quadrivacancy-substitutional oxygen complexes. The two-component data are analyzed using an extension of the trapping model to obtain the positron trapping rates at these vacancy-type defects. The annealing of these defects is discussed.
Thermal Stability of B-Doped SiGe Layers Formed on Si Substrates by Si-GeH4-B2H6 Molecular Beam Epitaxy
Authors: Karasawa Takeshi , Yasuo Kunii Yasuo Kunii , Michiharu Tabe Michiharu Tabe
Published: February 2005

The thermal stability of B-doped SiGe layers formed on Si substrates is studied, using samples prepared by Si-GeH4-B2H6 molecular beam epitaxy. Strain relaxation and the diffusion of Ge and B in the samples are measured after heat treatment corresponding to heterostructure bipolar transistor (HBT) fabrication processes. The strain in the SiGe layer remains almost constant during annealing at up to 950°C for 30 min, while some misfit dislocations are formed above 800°C in samples with relatively high Ge content (>10 at.%). Ge diffusion is negligible up to 950°C, but B atoms diffuse considerably even if the temperature for 30 min annealing is as low as 850°C. Accordingly, the formation of misfit dislocations and B diffusion are the dominant factors limiting the Ge content and thermal treatments in HBT processes.
Growth Mechanisms and Properties of Coiled Whisker of Silicon Nitride and Carbon*
Authors: Iwanaga Hiroshi , Kawaguchi Masayuki , Motojima Seiji
Published: February 2005

This paper reviews recent studies of regularly coiled whiskers of Si3N4 prepared by the chemical vapor deposition (CVD) method as well as those of carbon by the catalytic pyrolysis method. Coiled Si3N4 whiskers have been obtained from a gas mixture of Si2Cl6 and NH3 at 1200°C on substrates on which metal impurity was painted. The most effective impurity for the growth of the whiskers was Ni for the quartz substrate and Fe for the graphite. A vapor liquid solid (VLS) growth mechanism was suggested from morphology of the whiskers. Coiled carbon whiskers have been grown by the catalytic pyrolysis of acetylene at 300-750°C using Ni powder as a catalyst. A small amount of H2S was indispensable for the growth of the coiled carbon whiskers. A Ni compound seed observed on the tip of the pair-coiled carbon whisker is a single crystal. It is suggested that each crystal plane of the Ni compound seed has a different catalytic ability for the growth of the coiled carbon whiskers. The growth mechanism for the coiled carbon whiskers involves the surface diffusion of carbon atoms on the Ni compound seed. Structure of the coiled whiskers of Si3N4 and carbon was investigated by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Furthermore, extension characteristics of these whiskers were examined.
Reflection High-Energy Electron Diffraction of Heteroepitaxy in Chemical Vapor Deposition Reactor: Atomic-Layer Epitaxy of GaAs, AlAs and GaP on Si
Authors: Kitahara Kuninori , Masashi Ozeki Masashi Ozeki , Kazuo Nakajima Kazuo Nakajima
Published: February 2005

We developed an observation technique of reflection high-energy electron diffraction (RHEED) for chemical vapor deposition (CVD). Using this technique, growth procedures of GaAs, AlAs and GaP on Si substrates, including thermal cleaning of Si, prelayer deposition and initial stage of growth, were examined. The growth was done applying atomic layer epitaxy in a CVD reactor. Then the origin of three-dimensional island growth on Si was studied. To separate the effects of lattice mismatch and those originating from the Si surface, growth of GaAs/GaP and GaP/GaAs was also examined. We concluded that the island growth at the initial stage was not directly induced by the lattice mismatch but by unintentional adsorption of intrinsic atoms onto the Si surface. The surface morphology was improved by depositing a prelayer at an optimum temperature of 850°C and growing an AlAs buffer layer.
Influence of Rapid Thermal Annealing on the Properties of Strained GaInAs Quantum Well Lasers
Authors: Maurel Philippe , Julien Nagle Julien Nagle , Jean Pierre Hirtz Jean Pierre Hirtz
Published: February 2005

The influence of rapid thermal annealing on the properties of GaInAs strained quantum well lasers is studied. Photoluminescence performed at 300 and 77 K shows that an optimum is found for annealing at 800°C-10 s. The threshold current density of the laser decreases by a factor of 2 to 3 while its internal quantum efficiency increases from 30% up to 60%. The origin of the non radiative traps involved in the process is discussed.
Nitride-Masked Polishing (NMP) Technique for Surface Planarization of Interlayer-Dielectric Films
Authors: Yoshihiro Hayashi Yoshihiro Hayashi , Shuji Takahashi Shuji Takahashi
Published: February 2005

A reflowed borophosphosilicate glass (BPSG) film having surface ridges is polished with a colloidal silica slurry, and the ridge width effect on the planarization rate or the efficiency is investigated. The planarization rate decreases drastically with increasing ridge width; thereby it is impossible to effectively remove the wide ridges corresponding to the stacked-type memory cell array areas in a dynamic random access memory (DRAM) device. Then, a nitride-masked polishing (NMP) technique is developed in which the BPSG surface except for the ridge areas, is covered with a Si3N4 film and the ridges are selectively polished away. A BPSG film on a DRAM with stacked-type capacitors is planarized by NMP to insure a tight focus margin for photolithography below deep submicron processes.
Electrical Properties of Langmuir-Blodgett Passivation Film for Hg1-xCdxTe
Authors: Kengo Shimanoe Kengo Shimanoe , Masao Sakashita Masao Sakashita
Published: February 2005

The electrical properties of the metal insulator semiconductor (MIS) structure of Hg1-x
Cd
x
Te (MCT, x=0.2 and 0.3) passivated by Langmuir-Blodgett (LB) films have been investigated. The insulation film is formed by photo-polymerized LB films of 10,12-heptacosadiynoic acid on an electrochemically reduced MCT surface. From the linear dependence of the reciprocal capacitance on the amount of LB films, the dielectric constant of the LB film is evaluated to be 2.95. The dispersion of capacitance under the accumulation condition is very small in the frequency range between 1 kHz and 2 MHz. The surface on n-Hg0.7Cd0.3Te is slightly accumulated at zero bias and has a surface state density of 2×1011 cm-2 eV-1 at the midgap. On the other hand, that of p-Hg0.7Cd0.3Te is slightly depleted and has a surface state density of less than 1×1011 cm-2 eV-1. The small hystereses in flatband voltage are 0.001 V and 0.02 V, corresponding to trap densities of 1.1×108 cm-2 and 1.7×109 cm-2 for n- and p-Hg0.7Cd0.3Te, respectively.
Effects of Ce Doping on Electronic Structures of Ln2-xCexCuO4 (Ln=Nd, Sm, Eu, Gd) Studied by Core-Level Photoemission Spectroscopy
Authors: Ishii Hiroyoshi , Koshizawa Takehito , Takaaki Hanyu Takaaki Hanyu , Shigeo Yamaguchi Shigeo Yamaguchi
Published: February 2005

We have investigated the changes in the electronic structures of Ln2-x
Ce
x
CuO4 (Ln=Nd, Sm, Eu and Gd) upon Ce doping using core-level X-ray photoemission spectroscopy. For Ln2-x
Ce
x
CuO4, the O 1s spectra exhibit a single-peaked structure. The energy positions of the O 1s lines are shifted toward the high binding energy side with increasing Ce concentration. For the Cu 2p spectra, the intensity ratio of the satellite to the main peaks decreases with increasing Ce concentration. This decrease can be explained by the presence of Cu1+ under Ce doping.
Superconducting Bi2Sr2Ca1Cu2O8+y Glass-Ceramics with Different Melting Histories
Authors: Lee Won-Hyuk , Kondo Hisao , Hideo Hosono Hideo Hosono , Yoshihiro Abe Yoshihiro Abe
Published: February 2005

Superconducting Bi2Sr2Ca1Cu2O8+y
glass-ceramics were prepared by controlled crystallization of the corresponding composition glasses. We examined the effect of melting temperature (T
m) of the glasses on the crystallization behavior and the T
c of the resulting glass-ceramics. The crystallization behavior was considerably influenced by the Cu(II)/ΣCu ratio of the precursor glass, which varies to a considerable extent with T
m. The lower Cu(II)/ΣCu ratio of the glass leads to formation of larger crystallites and higher excess oxygen absorption upon crystallization. The T
c of the glass-ceramics obtained by the same heat treatment tends to increase with increasing T
m of the mother glasses. This tendency of T
c to increase may be explained in terms of oxygen content in the glass-ceramics.
Generation of Phase Conjugate Wave from a Visible InGaAlP Laser
Authors: Awaji Yoshinari , Sayama Shuji , Suzuki Hiromasa , Teramachi Motoichi Ohtsu
Published: February 2005

This paper presents the first quantitatively measured results of detuning and spatial characteristics of the phase conjugate wave which is emitted from a Fabry-Perot cavity-type InGaAlP laser. Bandwidth of a nearly-degenerate four-wave mixing was confirmed to be due to the relaxation oscillation frequency of the laser. The reflectivity of the phase conjugate mirror and the amplification gain were larger than 10 and 100, respectively. By the off-axial injection of the probe beam to a broad stripe laser, the emitted phase conjugate wave was separated spatially from the pump beam. Non-degenerate four-wave mixing characteristics of an AlGaAs laser were also measured for the first time. Its 3-dB cutoff frequency was as large as 0.1 THz, which was determined by the reciprocal of the half-cycle time of the intracavity light-wave.
Theoretical and Experimental Evaluation of the Effect of Adding a Heat-Bypass Structure to a Laser Diode Array
Authors: Murata Setsuko , Hiroshi Nakada Hiroshi Nakada , Tetsuo Abe Tetsuo Abe
Published: February 2005

Because heat transferred between closely spaced elements in a compact laser diode array shortens array lifetime and affects the elements' operating characteristics, we theoretically and experimentally evaluated the effect of a heat-bypass structure by calculating and measuring the thermal resistance of array elements. Three-dimensional boundary element analysis showed that the heat bypass reduces the thermal resistance by an amount that is independent of cavity length. Measured junction voltages and wavelengths for a 50-µm-spaced 8-beam laser diode array with 600-µm-long cavities showed that the bypass structure reduces the thermal resistance resulting from simultaneous operation of all eight elements by more than 40%. And that the reduction is greatest for elements whose thermal resistance is highest. The resultant reduction in the junction temperature of array elements operating at 100 mW should increase array lifetime at least threefold.
Effects of Heat Treatment on the Sensitivity of Warm Carrier Devices for CH3OH Laser Radiation
Authors: Yasuoka Yoshizumi , Shimizu Takashi , Harakawa Kenichi , Gamo Kenji , Namba Susumu
Published: February 2005

Warm carrier infrared laser detectors, which have 0.1 µm-diameter ohmic contact electrode, were fabricated using a focused ion beam, and the effects of heat treatment on the detection sensitivity of the devices were studied at the CH3OH laser frequency. It was found that the sensitivity of the device increased by 100 times with heat treatment at 450°C.
Optical Constants of TiC0.95, VC0.86 and NbC0.93 from 0.8 to 80 eV
Authors: Koide Tsuneharu , Shidara Tetsuo , Fukutani Hirohito , Fujimori Atsushi , Otani Shigeki , Ishizawa Yoshio
Published: February 2005

The normal-incidence reflectance of single crystals of TiC0.95, VC0.86 and NbC0.93 was measured over a wide energy range between 0.5 and 100 eV. The optical constants in the 0.8-80-eV region are reported; they were deduced from a Kramers-Kronig analysis of the reflectance data by correcting for a surface-roughness effect using the measured roughness values. A numerical data table of the optical constants is also presented for TiC0.95.
X-Ray Spectroscopic Studies of Potassium Halides
Authors: Chikara Sugiura Chikara Sugiura , Hiroyuki Yamasaki Hiroyuki Yamasaki
Published: February 2005

The Kα emission and Kβ emission spectra in the fluorescence of K+ in KF, KCl, KBr and KI are measured with a two-crystal vacuum spectrometer. The satellite Kα′′ is observed for KBr and KI, while its presence is indistinct in KF and KCl. The measured Kβ5 peak is shifted toward higher energies from KF to KI in the range of 3.6 eV. The Kβ5 emission bands are presented along with the ultraviolet photoelectron spectra of the anion p-like valence bands, the K+ K absorption spectra and the K+ L2,3 absorption spectra of potassium halides, reported previously. With these spectra and optical-gap data, the first shoulder and two sharp peaks of the K+ L2,3 absorption spectra are identified as being due to core excitons, the energy levels of which are formed below the bottoms of their conduction bands. The binding energies of the excitons are estimated.
Electrical and Electromechanical Properties of Hot-Pressed Pb(Fe1/2Nb1/2)O3 Ferroelectric Ceramics
Authors: Masaru Yokosuka Masaru Yokosuka
Published: February 2005

Dense ceramics of Pb(Fe1/2Nb1/2)O3 with high resistivity were fabricated below 1000°C by making use of the hot-pressing technique. For these hot-pressed specimens, measurements of the spontaneous polarization, dielectric constants, electromechanical coupling factors, piezoelectric constants and elastic compliance constants were carried out as a function of temperatures between -30°C and 200°C. Temperature variations of the resistivity and linear thermal expansion were also studied. At room temperature, the following values were obtained: ε33
T/ε0=2640, P
s=11.3 µC/cm2, k
33=0.266, d
33=145×10-12 C/N and s
33
E=12.3×10-12 m2/N. These values were briefly compared with those of BaTiO3 ceramics.
Physico-Chemical Characterization of Na3Zr2Si2PO12 Fine Powders Prepared by Sol-Gel Method Using Citrates
Authors: Choy Jin-Ho , Han Yang-Su , Kim Yoon-Ho , Suh Kyung-Soo
Published: February 2005

Sodium superionic conductor (NASICON) powders have been prepared by sol-gel technique using citrates. The optimum pH condition (\cong6) for sol-gel process was predicted by theoretical consideration of thermodynamic equilibrium constants for corresponding metal salts in aqueous solution. The pure NASICON phase with rhombohedral unit cell could be obtained by thermal decomposition of citrate precursors at a relatively low temperature (850°C). When the calcining temperature was raised to 1100°C, however, slight monoclinic distortion with formation of a trace of monoclinic ZrO2 was observed. Thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) technique, scanning electron microscopy (SEM) and 31P static and magic angle spinning (MAS) NMR have been used to characterize the calcined powders.
Study on dc and ac Switching Behavior in Liquid Crystal Displays with Polymer Boundaries using a 4-Component Circuit
Authors: Sugimura Akihiko , Takahashi Yutaka , Zhong-can Ou-Yang
Published: February 2005

A 4-component circuit is proposed to study the electric behavior of liquid crystal displays with polymer boundaries accompanying dc and ac voltage application. Two series components C
1 and R
1 are introduced to represent the capacitance and dielectric relaxation of a polymer boundary. Another two parallel components, R
0 and C
0, are used to take into account the bulk effect of liquid crystal layer. Transient currents induced by three types of switching of an applied voltage, single step, triangular and rectangular waveforms, are explained theoretically and experimentally. The theoretical results are in excellent agreement with the data from experiments. These provide the measurement method for obtaining the 4 components in a cell assembly. It is found that the effective voltage which is applied only to the bulk is different from an external applied waveform.
Elementary Chemical-Reaction Processes on Silicon Surfaces*1
Authors: Yoshinobu Jun , Tanaka Shin-ichiro , Nishijima Mitsuaki
Published: February 2005

Studies of the elementary chemical-reaction processes of atoms and molecules on Si surfaces, which have been performed mainly by the authors using high-resolution electron energy loss spectroscopy, are reviewed. The adsorbed states, adsorbed sites and adsorbed structures of atoms and molecules, in particular of H, O2, NH3, N and C2H2, and thermal decomposition processes of these adsorbates are discussed in detail. Recent studies utilizing scanning tunneling microscope and lasers, and trends in Si-gas reaction studies are also reviewed.
Main Peak Profiles of Total Reflection X-Ray Fluorescence Analysis of Si(001) Wafers Excited by Monochromatic X-Ray Beam W-Lβ (II)
Authors: Yakushiji Kenji , Ohkawa Shinji , Yoshinaga Atsushi , Harada Jimpei
Published: February 2005

In the mapping of trace metal impurities on a Si wafer by the total reflection X-ray fluorescent (TXRF) analysis with use of monochromatic W-Lβ radiation, the trace metal impurity peaks as well as a main peak profile show a drastic change even with a slight translation of the measurement position on the wafer surface. This phenomenon is shown to arise from multiple effects: in the TXRF system (Technos TREX-610) the measurement point is adjusted by movements based on the polar coordinates and the incident X-ray beam is diffracted in the direction of the detector with high intensity when the Bragg-reflection condition is satisfied [I. Yakushiji et al.: Jpn. J. Appl. Phys. 31 (1992) 2872]. X-ray fluorescent peaks of Fe-Kα and Ni-Kα radiations with very small intensity were found to be influenced by the intensity of the W-Lβ radiation detected by the X-ray fluorescent detector. It is pointed out that this is very important in estimating the accuracy of the measurement data.
X-Ray Photoelectron Spectroscopic Study of Oxidation of InP II: Thermal Oxides Grown at High Temperatures
Authors: Noboru Shibata Noboru Shibata , Hideaki Ikoma Hideaki Ikoma
Published: February 2005

A previous X-ray photoelectron spectroscopic (XPS) study on oxidation of InP was extended to thermal oxides grown at higher temperatures (400°C and 700°C). The chemical compositions and depth distributions of these thermal oxides are essentially the same as those reported earlier for native and chemical oxides. Hence, the oxidation model we have proposed is also applicable to the oxides grown at higher temperatures (>400°C). XPS analysis was performed for native oxide grown on the substrate which was not subjected to heat treatment such as ohmic contact annealing, and whoes surface stoichiometry was considered to be maintained. The results showed the dominance of In2O3 near the oxide-InP interface, indicating that the depletion of P from the InP surface was not the reason for the formation of In2O3 in the first stage of oxidation. Indium is thus considered to be more readily oxidized than phosphorus.
Effects of External Stresses on the Low Temperature Thermal Oxidation of Silicon
Authors: Tamura Takao , Tanaka Naoya , Tagawa Masahito , Nobuo Ohmae Nobuo Ohmae , Masataka Umeno Masataka Umeno
Published: February 2005

Thermal oxidation of silicon was conducted under the application of external compressive or tensile stress at relatively low oxidation temperature. The effect of external stress appeared in different ways depending on the oxidation temperature. While the stress effect of oxidation at 800°C was well interpreted with the linear-parabolic oxidation model (L-P model), that at a temperature lower than 700°C contradicted the L-P model and strongly suggested the existence of an oxidation reaction of interstitial silicon atoms in the oxide.
Detection of Hydrogen on Nickel (110) Surface by Electron-Stimulated Desorption
Authors: Akemi Takano Akemi Takano , Kazuyuki Ueda Kazuyuki Ueda
Published: February 2005

Hydrogen on a nickel (110) surface was investigated by means of an electron-stimulated desorption (ESD) technique in ultrahigh vacuum. The ESD-H+ yield increased with exposure time to a residual gas pressure of 8×10-11 Torr at surface temperatures below 400 K. The yield was decreased by electron beam irradiation for a certain period and increased again after irradiation ended. The rate of increase was slower at lower specimen temperatures. The Arrhenius plot of the rate of increase indicates that there is an activation barrier of 0.046 eV required for increasing the amount of hydrogen on the surface. This result is explained by the segregation of hydrogen from a subsurface region.
Fabrication and Characterization of Comb-Shaped Lateral Field-Emitter Arrays
Authors: Itoh Junji , Tsuburaya Kazuhiko , Kanemaru Seigo , Watanabe Teruo , Itoh Shigeo
Published: February 2005

A new lateral field-emitter array (FEA) has been fabricated and its structural parameters affecting the emission characteristics have been investigated. The present FEA consists of an emitter made of a tungsten thin film (0.2-0.6 µm) and a gate electrode self-aligned to the emitter with submicron spacing (0.3-0.7 µm). The emitter has an array of rectangular tips with 3-µm-wide edges; the emitter looks like a comb when viewed from above. We have measured the dependence of the emission characteristics on structural parameters such as pitch (p), emitter-to-gate spacing (g) and emitter thickness (t). It was found from experimental results that the characteristics were strongly dependent on the above parameters, especially on the p/w ratio (w is the edge width; 3 µm). An emission current of 2 µA/tip was obtained at a gate voltage of 110 V with FEA of p/w=3.3, g=0.3 µm and t=0.2 µm. In this paper, the fabrication process and emission characteristics including stability are described in detail.
Elastic Scattering of Low-Energy Electrons, Positrons and Protons in Copper
Authors: Kawata Kaoru Ohya
Published: February 2005

Total cross section (TCS) and differential cross section (DCS) are calculated using the partial wave method for the elastic scattering of 0.1 eV-1 keV electrons, positrons and protons in solid copper. At low energies, because of the cancellation of the electrostatic potential by the polarization of a copper atom bound in the solid and the absence of an exchange effect, the TCS for positrons is much smaller than that for electrons, whereas the TCSs for positrons and for electrons are comparable at the highest energy (1 keV). The DCS for electrons shows oscillatory behavior, and the DCS for positrons is smooth, the minimum being found at the forward direction. The DCS for protons dramatically increases for very small scattering angles near zero degrees, whereas the DCS is equal to that of positrons for angles larger than 30°(>10 eV).
Effects of Electric Field on the Molecular Orientation in Evaporated Ferroelectric Vinylidene Fluoride and Trifluoroethylene Copolymer Films
Authors: Yoshida Yuji , Toshihisa Horiuchi Toshihisa Horiuchi , Kazumi Matsushige Kazumi Matsushige
Published: February 2005

An electric field was applied during the evaporation process to obtain ferroelectric polymeric ultrathin films with uniaxial dipole orientation. The crystal structure and molecular orientation in the evaporated (VDF/TrFE) copolymer films were examined with a recently developed total reflection X-ray diffractometry, revealing that polar Form I crystals with the dipole moment oriented normal to the substrate can be formed by evaporating the samples under a high electric field (6 MV/m). Moreover, we evaluated the ferroelectric-paraelectric phase transition behavior of the evaporated films from a structural viewpoint.
Development of Microwave Control in Pulsed-ESR Apparatus
Authors: Mizuta Yukio , Masahiro Kohno Masahiro Kohno , Kanae Fujii Kanae Fujii
Published: February 2005

In order to diminish the deadtime and remove the unwanted signals in the pulsed-ESR measurement, a new four-port phase switching circuit and main/slave switching circuit were developed and attached to the pulsed-ESR microwave circuit. Moreover, the gate of a travelling-wave-tube amplifier (TWTA) was shared to accommodate each main pulse in order to perform the multiple pulse experiment for a duration beyond the limitation of a single TWTA gate. These fabrications were very effective in the pulsed-ESR measurement.
Formation of Pt Interconnection Lines and Periodic Structures
Authors: Bergh Carlos Garrido
Published: February 2005

Laser-induced chemical vapor deposition (LCVD) has been used to produce platinum lines on pyrex glass substrates by means of the platinum bis-hexafluoro-acetylacetonate as precursor. The effect that writing speed has on the line geometry and resistivity is studied, as well as the influence of the writing speed, precursor vapor pressure and laser power on the periodic structures formation. The results are discussed in terms of the laser beam residence time and the radiation-induced temperature increase. It is possible to obtain lines with a resistivity very close to that of pure platinum under optimum experimental conditions.
Deformability in Hardened and Normal Erythrocytes during Sedimentation Process
Authors: Toyama Yoshiharu , Dobashi Toshiaki , Idonuma Atsuko , Cerny Akio Sakanishi
Published: February 2005

In order to clarify the effect of erythrocyte deformability on the sedimentation rate, we have measured the sedimentation curve of hardened swine erythrocytes in a saline solution and have compared it with that of normal erythrocytes. The observed length of the medium along the vessel was linearly proportional to the sedimentation period. The initial slope v of the sedimentation curve decreased with increase in the volume fraction of erythrocytes. Sedimentation rate v of hardened erythrocytes was comparable to that of normal ones at low volume fractions, but was smaller at high volume fractions. These experimental data were analyzed with a theoretical formula developed by Oka Biorheology 22 (1985) 315, resulting in a deformability factor of f=0.99 for hardened erythrocytes. This value of f is reasonable for such rigid cells and is much larger than the value for normal erythrocytes, approx. 2/3.
Limits and Possibilities of Miniaturization
Authors: H. Rohrer H. Rohrer
Published: February 2005

Miniaturization has progressed exponentially over the past couple of decades, and there is no reason to believe that it should not continue to do so in the near future, say one to two decades. After that we can foresee two distinct periods of miniaturization. The first one will involve fundamentally new effects and phenomena, e.g. when the dimension becomes comparable to or smaller than characteristic length scales. In the second, when the scale of a few nanometers is reached, classical miniaturization or the division into ever smaller elements will come to an end. A possible scenario for this “post-miniaturization” period is one of assemblies of functional elements into complex functional units. Miniaturization is, so to speak, superseded by complexity. This development is certainly a formidable scientific and technological challenge. The major issue, however, will be how society can and will cope with it.
Atomic-Scale Chemistry of Metal Surfaces
Authors: Ken-ichi Tanaka Ken-ichi Tanaka
Published: February 2005

The idea of pseudo-molecules is deduced from reviewing the results of scanning tunneling microscopy (STM) of metal surfaces. Ni(110), Cu(110), and Ag(110) surfaces exposed to H2 or O2 at room temperature reveal the formation of one-dimensional pseudo-molecules, which is essentially different from the phenomenon of adsorption. The pseudo-molecules produced on the surface are in an ordered arrangement on these metal surfaces, where the arrangement is influenced by their lateral interaction. The -Cu-O- chains oriented along the <001> direction coalesce to form a p(2×1) arrangement on the Cu(110), but the added -Ag-O- rows on the Ag(110) surface may not prefer the p(2×1) structure, because the p(2×1) -Ag-O- added row induces a large distortion of the substrate Ag atoms. As a result, the added -Ag-O- rows undergo sequential change of the p(n×1) structures. When the p(2×1) -Cu-O- island is annealed at 550-640 K, the p(2×1) overlayer bunches into regular-sized in-phase p(2×1) -Cu-O- islands. In contrast, reordering of the (2×1) -Ag-O- overlayer to (4×1) at 500 K yields narrow out-of-phase (4×1) domains with the wavering domain boundaries. Based on these results, the influence of pseudomolecules on catalysis is predicted.
Dynamics of Atomically Thin Layers-Surface Interactions in Tip-Substrate Geometry
Authors: H. Rafii-Tabar H. Rafii-Tabar , Y. Kawazoe Y. Kawazoe
Published: February 2005

Nano-scale point-contact experiments involving the interactions of atomically-sharp tips with metallic substrates (akin to the STM and AFM configurations) have revealed that the physiosorption of an atomically-thick monolayer film on the surface of a substrate leads to the lowering of the force of adhesion between the tip and the surface. We have carried out large-scale constant-temperature molecular dynamics (MD) simulations based on the Nose-Hoover constraint formalism and using many-body inter-atomic potentials of Finnis-Sinclair type to show, at the atomistic level, the mechanisms contributing to the above phenomenon. We show that, irrespective of whether the wetting phenomenon occurs between the tip and the adsorbed monolayers, the force of adhesion is always reduced relative to the case of an atomically clean surface. The results of our computer-based simulation studies seem to be in agreement with similar point-contact experimental investigations. An analytic model, based on contact angle theories, is developed to give an inter-pretation of the simulation results.
Structure of the Bi/Si(111) Surface by Field-Ion Scanning Tunneling Microscopy
Authors: Park Chan , Bakhtizin Raouf Z. , Tomihiro Hashizume Tomihiro Hashizume , Toshio Sakurai Toshio Sakurai
Published: February 2005

A combination of LEED and FI-STM has been used to characterize the Bi/Si(111) system. Two distinct phases of the √3×√3 structure formed on the Si(111) surface are imaged for the first time by STM and are studied as a function of coverage. Trimers of Bi atoms are clearly resolved at 1 ML whereas single Bi atom adsorption are documented at 1/3 ML. The atomic geometry of these structures and the development of two phases as a function of coverage are discussed.
Effects of Organometallic Compounds Introduced to Plasma on Diamond Synthesis
Authors: Ichinose Hiromichi , Nibu Yoshinori , Katsuki Hiroaki , Masamitsu Nagano Masamitsu Nagano
Published: February 2005

Volatile organometallic compounds were introduced to feed gas (CH4/H2) during the synthesis of diamond by microwave plasma chemical vapor deposition. Addition of Si(CH3)4, Sn(CH3)4, Sn(CH3)4, Fe(AA)3, TiO(AA)2or Zr(AA)4increased nucleation density of diamond particles to 2-10 times that without additives. Addition of Zr(AA)4and TiO(AA)2made the grain sizes smaller. Most additives lowered atomic hydrogen temperature, increased concentration of C2in plasma and seemed therefore to degrade the crystallinity of the diamonds. Some additives shifted the A band cathodoluminescence to a higher energy region. In the case of Si(CH3)4, the GR-1 center cathodoluminescence was observed as well as the A-band, and adhesion of the diamond film was markedly improved.
Nanotribology and the Stability of Nanostructures
Authors: Landman Uzi , Luedtke W. D. , J. Ouyang J. Ouyang , T. K. Xia T. K. Xia
Published: February 2005

Atomic scale energetics, structure, and formation mechanisms of solid and liquid junctions occurring between a solid metal tip and a clean metal surface or between the tip and a liquid film of hexadecane molecules adsorbed on a solid surface, are investigated using large-scale molecular dynamics simulations. Additionally, structural and dynamical properties of adsorbed hexadecane films of variable thickness are discussed. Upon approach of the tip toward the surface a jump-to-contact phenomenon leads to the formation of an adhesive contact between the two. The solid intermetallic junctions exhibit crystalline structure and their elongation mechanism, upon slow retraction of the tip from the surface after contact, involves a sequence of plastic deformations and yield processes, coupled with structural rearrangements. The molecular liquid is layered in the capillary junction for small separations between the two confining solid surfaces. Further separation results in a transition to a liquid-like region in the middle of the elongated liquid column. Investigations of the molecular scale origins of capillary liquid junction formation, as well as consequences of solid and liquid junctions for force measurements via atomic force microscopy, are discussed. A brief discussion of the mechanism of collapse and spreading of a gold nano-droplet deposited on a nickel surface is included.
Scanning Tunneling Microscopy Studies of Semiconductor Surface Passivation
Authors: Bringans R. D. , Biegelsen D. K. , J. E. Northrup J. E. Northrup , L.-E. Swartz L.-E. Swartz
Published: February 2005

Heteroepitaxial growth of compound semiconductors on Si surfaces is strongly affected by the bonding of the first atomic layer to the substrate. These effects, which include passivation, etching, reaction and compound formation, can be understood by examining the atomic structure of the surface as the first atomic layers of the overlayer are formed. In this paper we examine the information obtained from scanning tunneling microscopy for passivation of semiconductor surfaces. We will discuss in detail the case of group V and VI overlayers on Si surfaces and also address the passivating effect of group VI atoms on the surface of III-V compounds.
Luminescence from Strained Si1-xGex/Si Quantum Wells Grown by Si Molecular Beam Epitaxy
Authors: Fukatsu Susumu , Noritaka Usami Noritaka Usami , Yasuhiro Shiraki Yasuhiro Shiraki
Published: February 2005

Excitonic luminescence was observed from strained Si1-x
Ge
x
/Si quantum wells (QWs) grown on Si(100), (111) and (110) substrates using Si molecular beam epitaxy (Si MBE). Influence of growth environment and quality of the crystal on the luminescence efficiency is described. Quantum confinement of excitons was clearly indicated by the characteristic energy shift of luminescence peak energy with decreasing well width. The emission peak of QWs was found to be shifted to higher energies due to Ge segregation-induced potential profile distortion. This energy shift was effectively removed by the adoption of the segregant-assisted growth (SAG) scheme using an Sb adlayer. Room temperature electroluminescence was observed from strained Si0.65Ge0.35/Si QWs grown on both (100) and (111) substrates.