bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxynitridation of Silicon Using Helicon-Wave Excited and Inductively-Coupled Nitrogen Plasma
Authors: Yoshinaga Okamoto Yoshinaga Okamoto , Shinjiro Kimura Shinjiro Kimura , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Si was oxynitrized (and/or nitrized) in both helicon-wave-excited and inductively-coupled N2 or N2+Ar mixed plasma. Fairly good capacitance-voltage (C–V) characteristics were obtained after post-thermal annealing at 400°–500°C for 30 min in nitrogen ambient. X-ray photoelectron spectroscopic (XPS) measurements showed that chemically stoichiometric Si oxynitride, Si2 N2 O, was uniformly formed throughout the whole film thickness at a flow-rate ratio of N2 of 80% in a N2 + Ar mixed plasma (N2:Ar = 8:2). On the other hand, SiO2 was formed at the outer surface while Si2 N2O was formed in the middle portion of the film and near the interface between the grown film and Si, when the flow-rate ratio of N2 was less than about 80%. The growth rate and the degree of “nitridation" were maximum at flow-rate ratio of N2 of 80%. The leakage current in the film was found to be mainly the Fowler-Nordheim-type tunneling current.
Positive and Negative Ions in RF Plasmas of SF 6/N 2 and SF 6/Ar Mixtures in a Planar Diode
Authors: Shinya Sasaki Shinya Sasaki , Itsuo Ishikawa Itsuo Ishikawa , Kazuya Nagaseki Kazuya Nagaseki , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

Ionic species in 13.56 MHz discharge of SF6/N2 and SF6/Ar mixtures were measured by means of direct sampling using a quadrupole mass spectrometer. Dominant negative ions in the SF6/N2 discharge are F-, SF5
- and SF6
-, while the positive ions are SF3
+, SF5
+ and N2
+. In the SF6/Ar discharge the major ions are the same as in the SF6/N2 discharge except that N2
+ is replaced by Ar+. The signal intensity ratios of these ionic species depend on the ratio of N2 or Ar to SF6 in the discharge. In particular, the ratio of Ar to SF6 in the SF6/Ar discharge increases, the signal intensity ratio of SF3
+ to SF5
+ shows a concave variation, and the total intensity of negative ions decreases rapidly in the SF6/Ar discharge. These results in the SF6/Ar discharge are different from the variations in the SF6/N2 discharge, and seem to be based on the effects of the metastable atom Ar* on both production of SF3
+ and extinction of negative ions.
Effects of Ion Flow by E×B Drift on Dust Particle Behavior in Magnetized Cylindrical Electron Cyclotron Resonance Plasmas
Authors: Nunomura Shota , Noriyasu Ohno Noriyasu Ohno , Shuichi Takamura Shuichi Takamura
Published: October 2002

Interactions between poloidal ion flow associated with E×B drift and dust particles have been investigated in magnetized cylindrical electron cyclotron resonance plasmas, in which radial electric field is controlled by a biased ring-shaped electrode. The dust particles are spun out and removed from the plasma due to poloidal ion drag force, even when the inward electric force on the dust particles is larger than the gravitational force. This indicates the possibility of using a new method to remove the dust particles from the processing plasma. On the other hand, in order to sustain the dust particles in the plasma, the effects of this poloidal ion flow should be substantially reduced by the friction between the dust particles and neutral gas.
Dependencies of Transport and Photoluminescence on Morphology of Vacuum Deposited C60 Films
Authors: Keiichi Kaneto Keiichi Kaneto , Koichi Rikitake Koichi Rikitake , Takahiro Akiyama Takahiro Akiyama , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Electrical transport, its high field effects and photoluminescence are studied in C60 films deposited at various substrate temperatures. The morphology of films is characterized by X-ray diffraction and atomic force microscope. It is found that the electrical conductivity depends strongly on the morphology and the applied field. High conductivity is obtained for films prepared at high substrate temperatures and high fields. The emission peak shifts to the low energy side for highly crystalline films. The results are discussed in terms of the crystallinity and the delocalization of electrons.
Determination of Optical Constants of Two-Ply Phase Plate
Authors: Onaka Kengo , Mitsuo Yoshida Mitsuo Yoshida , Ryuichi Shintani Ryuichi Shintani
Published: October 2002

Optical properties of a laminated sheet are investigated as a two-ply film. Retardations of the laminated sheet could not be obtained without separating it into individual films. A new method presented here makes it possible to determine three optical constants of two-ply phase plates: two optical pass differences and their relative azimuth angle. Experimental values of known samples which are in agreements with calculated values are obtained by the new method.
Accurate Calculation of Collision Integrals Using Adaptive Methods
Authors: Yau-tang Gau Yau-tang Gau , Shuang-fa Guo Shuang-fa Guo
Published: October 2002

In this work, we have developed accurate and efficient methods for calculating the scattering angle, time integral and electronic energy loss for binary collisions in matter. In contrast to the conventional integration and the hard sphere approximations, our new time integral is obtained by calculating the difference between the distance to the target atom and the ion path length. To compute the scattering angle and time integral accurately and efficiently, an adaptive Simpson quadrature using a smoother integrand is adopted. The energy loss arising from the local electron-concentration-dependent electronic stopping power is obtained by tracing the ion trajectory. To reduce the computation time, a second-order differential equation for the ion motion using an adaptive Runge-Kutta-Fehlberg algorithm is developed.
Visible Luminescence Induced by Si-Ion Implantation into Si Single Crystals Covered with a Thin SiO2Layer
Authors: Lan Aidong , Baixin Liu Baixin Liu , Xinde Bai Xinde Bai
Published: October 2002

An investigation of Si ion implantation into Si single crystals covered with a SiO2layer of various thicknesses (1000–3000 Å) was conducted and new characteristic luminescence bands were observed. A visible band that peaked around 1.89 or 2.0 eV was observed from the as-implanted samples. After high temperature post annealing, a visible band located in the range of 1.7 eV was detected. Interestingly, a new luminescence band around 1.5 eV was observed, for the first time, in a sample covered with a 3000 Å SiO2layer, after high dose implantation and annealing. We report, in this letter, the experimental results and a brief discussion concerning the various possible mechanisms responsible for the observed luminescence bands.
A Novel Decagonal Quasicrystal in Zn-Mg-Dy System
Authors: Taku J. Sato Taku J. Sato , Eiji Abe Eiji Abe , An Pang Tsai An Pang Tsai
Published: October 2002

A decagonal quasicrystal has been newly found in a conventionally solidified Zn70Mg20Dy10alloy. The decagonal phase was observed in an annealed state, and thus is likely to be thermodynamically stable. As seen in the electron diffraction patterns, the decagonal phase has a novel local structure in comparison to previously-observed decagonal-phases.
Ultrawideband Filter for Noise Control
Authors: Halevi M. S. Kushwaha
Published: October 2002

The purpose of this letter is to propose a tandem structure that allows to achieve an ultrawideband filter for noise within the human audible range of frequencies.
The Field Emission Characteristics of a-C:H Thin Films Prepared by Helical Resonator Plasma Enhanced Chemical Vapor Deposition
Authors: Rho Soon Joon , Shim Jae Yeob , Chi Eung Joon , Lee Hong Koo Baik
Published: October 2002

The field emission characteristics of hydrogenated amorphous carbon (a-C:H) films prepared by helical resonator-plasma enhanced chemical vapor deposition (HR-PECVD) are examined. a-C:H films are deposited with CH4/H2 and CH4/Ar gases under different substrate RF bias conditions. The properties of a-C:H films are investigated by Raman spectroscopy, Fourier transform IR (FT-IR), UV spectroscopy and elastic recoil detection (ERD). Field emission characteristics of a-C:H coated on Si whiskers which are grown by the vapor-liquid-solid (VLS) method are tested under ultrahigh vacuum. Highly efficient field emission characteristics are achieved in the specimen deposited at a substrate RF bias higher rather than in the ground deposition condition regardless of the nature of the reactant gas. As the substrate RF bias is changed from ground to a higher RF substrate bias, the deposited a-C:H films have lower hydrogen contents and higher sp2-bonds. Therefore, the field emission characteristics of a-C:H thin films are affected by the hydrogen contents of the films rather than by the sp3/sp2 ratio.
Theoretical Investigations of Thermodynamic Stability of III-III-N Semiconductor Alloys
Authors: Tomonori Ito Tomonori Ito
Published: October 2002

Excess energies and lattice parameters of III-III-N semiconductor alloys, including AlN, GaN and InN, are calculated using a pseudopotential perturbation approach in order to investigate thermodynamic stability. Calculated excess energies of In0.5Ga0.5N, In0.5Al0.5N and Al0.5Ga0.5N with hypothetical chalcopyrite structures have positive values. This result implies that these solid solutions are thermodynamically unstable at 0 K. Validity of Stringfellow's DLP model for semiconductor alloys including them is ascertained based on the calculated excess energies and equilibrium lattice parameters. Using these excess energies, the miscibility gap at high temperatures is discussed by considering free energies.
High-Quality Boron-Doped a-SiC:H Film by Post-Hydrogen Treatment Using a Mercury-Sensitized Photochemical Vapor Deposition Method and Its Application to a-Si:H Solar Cells
Authors: Jae Hoon Jang Jae Hoon Jang , Koeng Su Lim Koeng Su Lim
Published: October 2002

Post-hydrogen treatment of boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) film using a mercury-sensitized photochemical vapor deposition (photo-CVD) method was proposed as a novel method to improve film quality. The activation energy of the hydrogen-treated film decreased from 0.467 eV to 0.441 eV and its conductivity increased from 3.7×10-7 Scm-1 to 6.5×10-7 Scm-1 as the hydrogen treatment time increased from 0 (without hydrogen treatment) to 30 minutes. These film changes are thought to occur in the bulk of the boron-doped a-SiC:H film. When this method was applied to the boron-doped a-SiC:H layer of pin-type amorphous silicon solar cells, the open circuit voltage and fill factor increased without causing a decrease in the short circuit current, resulting in a conversion efficiency enhancement of about 7%. This improvement in the cell performance can be explained by an increase in the built-in potential of the cell due to a decrease in the activation energy of the p-layer.
High Performance DC Superconducting Quantum Interference Device Utilizing a Bicrystal Junction with a 30° Misorientation Angle
Authors: Minotani Tadashi , Kawakami Satoru , Kiss Takanobu , Yukinori Kuroki Yukinori Kuroki , Keiji Enpuku Keiji Enpuku
Published: October 2002

A high T
c dc superconducting quantum interference device (SQUID) was fabricated using a bicrystal junction with a misorientation angle of θ=30°. The junction with a width of 2 µ m exhibited high resistance R
s=10 Ω and critical current I
0=25 µ A at T=77 K. This gives a I
0
R
s as high as 250 µ V. These values indicate that the bicrystal junction has great potential for the development of high performance SQUIDs. The SQUID fabricated with a 30° junction exhibited voltage modulation depths as high as ΔV=85 µ V, 40 µ V and 20 µ V at T=77 K for the inductance values of L
s=60 pH, 100 pH and 160 pH, respectively. These are the highest values reported so far. Preliminary noise measurement showed that the flux noise of the SQUID is less than 8 µΦ0/ Hz1/2 for the white noise region, and less than 70 µΦ0/ Hz1/2 at f=1 Hz when the 60 pH-SQUID is dc biased and operated with a conventional Flux Locked Loop (FLL) circuit.
Relationship between Crosstalk and Readout Magnetic Field Direction on Trilayer Magnetically-Induced Super Resolution Media
Authors: Tamanoi Ken , Tanaka Tsutomu , Sugimoto Toshio , Koji Matsumoto Koji Matsumoto , Keiji Shono Keiji Shono
Published: October 2002

Land/groove recording was conducted on the trilayer double-mask MSR media. A CNR of 47 dB was obtained for a mark length of 0.33 µ m and track pitch of 0.7 µ m. The crosstalk was negligibly low when the readout magnetic field was applied in the writing direction. Random jitter was 10%, even when the data were recorded on the adjacent tracks, assuming (1, 7)-RLL encoding. This implies that an areal density of 3.69 Gbits/inch2 is possible. The crosstalk changed drastically depending on the readout magnetic field direction. It was found that the area of the front mask was larger when the readout field was applied in the writing direction, compared to the readout field in the erasing direction. This explains the big difference in crosstalk due to the readout field direction.
Effective Production of Negative Ions around Magnetized CF4 Plasma Column
Authors: Ryoichi Kawai Ryoichi Kawai , Tetsu Mieno Tetsu Mieno
Published: October 2002

Mass distributions of negative and positive ions in a magnetized CF4 plasma column are simultaneously measured using the newly developed ion cyclotron resonance mass spectrometer. Strong accumulation of F- ions around the reactive plasma column is obtained using a mass spectrometer and the Langmuir probe method, which enables radial plasma confinement by the magnetic field to obtain suitable condition for producing and maintaining negative ions. Using this spectrometer, spectra of positive and negative ions are simultaneously and separately measured.
Ultrafast Photoconductive Detectors Based on Semi-Insulating GaAs and InP
Authors: Masahiko Tani Masahiko Tani , Kiyomi Sakai Kiyomi Sakai , Hidenori Mimura Hidenori Mimura
Published: October 2002

Photoconductive dipole antennas fabricated on semi-insulating (SI) GaAs and SI-InP were used to detect terahertz (THz) pulses. The responses of these long-carrier-lifetime photoconductive detectors were compared to that of the photoconductive antenna fabricated on a low-temperature grown GaAs (LT-GaAs) with a subpicosecond carrier lifetime. The SI-InP-based photoconductive detector showed a higher responsivity and a better signal-to-noise ratio (SNR) than the LT-GaAs-based photoconductive detector at low gating laser powers. The SI-GaAs-based detector, however, showed a responsivity comparable to that of the LT-GaAs photoconductive detector only at very weak gating laser power, and the SNR of the SI-GaAs-based detector was poor for overall gating laser powers due to the high background noise originating from a large amount of stray photocurrent.
Mn-Activated CaO–Ga2O3 Phosphors for Thin-Film Electroluminescent Devices
Authors: Minami Tadatsugu , Yamada Hiroyuki , Yoshihiro Kubota Yoshihiro Kubota , Toshihiro Miyata Toshihiro Miyata
Published: October 2002

Multicomponent oxide phosphors such as Mn-activated CaO–Ga2O3 are demonstrated to be very promising as the thin-film emitting layer for thin-film electroluminescent (TFEL) devices. The EL emission color from CaO–Ga2O3:Mn TFEL devices changed from green to orange as the CaO content was increased from 0 to 100 mol%. A Ga2O3:Mn TFEL device driven at 1 kHz produced a green emission with a luminance of 232 cd/m2. A yellow emission with a luminance of 1725 and 261 cd/m2 was obtained in a TFEL device using a CaGa2O4:Mn thin film prepared with a CaO content of 50 mol%, when driven at 1 kHz and 60 Hz, respectively.
Lattice Distortion of Microcrystalline Cubic Boron Nitride Measured by X-Ray Diffraction
Authors: Masahiro Mieno Masahiro Mieno
Published: October 2002

Cubic boron nitride (c-BN) film synthesized by bias sputtering was studied using X-ray diffraction. The diffraction profile analysis indicated that the c-BN film consisted of microcrystals with apparent crystal sizes of about 34±4 Å. Furthermore, it was found that the lattice of microcrystals was distorted by elongation of over 1% toward the film surface direction. This variation could be caused by residual compressive stress lying in the film plane. The residual compressive stress was estimated to be of the order of 1011 dyne/cm2 using elastic theory.
Field Emission Patterns from Single-Walled Carbon Nanotubes
Authors: Saito Yahachi , Hamaguchi Koji , Nishino Tetsuo , Hata Koichi , Tohji Kazuyuki , Kasuya Atsuo , Nishina Yuichiro
Published: October 2002

A bulk bundle (with a diameter of about 100 µ m) of single-walled nanotubes (SWNTs), which were obtained after a purification process of carbon soot containing SWNTs, was used as an electron emitter. Many spikes of micro-bundles (with a typical diameter of 20–30 nm) of SWNTs extruded from the surface of the bulk emitter. Field emission originating from individual micro-bundles was observed on a fluorescent screen 50 mm apart from the tip. Each micro-bundle of SWNTs gave a corresponding bright spot, but no fine structure was observed within the bright spots. A probe hole device was used to measure an electron current from a single micro-bundle. The Fowler-Nordheim plot of the current and the applied voltage yielded a straight line, confirming the current results from field emission.
Site-Independent Adsorption of Hydrogen Atoms Deposited from a Scanning Tunneling Microscope Tip onto a Si(111)- 7×7 Surface
Authors: Kuramochi Hiromi , Uchida Hironaga , Kuwahara Yuji , Watanabe Kazuyuki , Aono Masakazu
Published: October 2002

When hydrogen atoms are deposited from a scanning tunneling microscope tip made of platinum onto a Si(111)-7×7 surface by means of field evaporation, the deposited hydrogen atoms are almost equally adsorbed to the `center' and `corner' silicon adatom sites of the 7×7 structure, in contrast to conventional thermal hydrogen atoms that are preferentially adsorbed to the `center' silicon adatoms. The possible origin of this difference is discussed.
Crystalline Properties of Laser Crystallized Silicon Films
Authors: Toshiyuki Sameshima Toshiyuki Sameshima , Keiko Saitoh Keiko Saitoh , Mitsuru Sato Mitsuru Sato , Akimitsu Tajima Akimitsu Tajima , Nobukazu Takashima Nobukazu Takashima
Published: October 2002

The carrier mobility of phosphorus-doped laser crystallized polycrystalline silicon (poly-Si) films was investigated. An analysis of the free carrier optical absorption spectra gave the carrier mobility, 6–11 cm2/V·s, for the laser energy between 140 (the crystallization threshold) and 280 mJ/cm2. The mobility increased as the temperature decreased from 473 K to 77 K because of the reduced carrier scattering by the lattice vibration as in single crystalline silicon. On the other hand, the carrier mobility obtained by the Hall effect measurements increased from 1 to 5 cm2/V·s as the laser energy increased. The mobility for samples crystallized near the crystalline threshold decreased as the temperature decreased from 473 K to 77 K. This is probably caused by lack of the thermal excitation energy for crossing the energy barrier at the grain boundary.
Diamond Growth by Dual Hollow Cathode Arc Chemical Vapor Deposition
Authors: Gou-Tsau Liang Gou-Tsau Liang , Franklin Chau-Nan Hong Franklin Chau-Nan Hong
Published: October 2002

A new design for a dual hollow cathode arc chemical vapor deposition system is used to grow diamond films. The inner hollow cathode is the primary thermionic emission source. The outer hollow cathode magnified the discharge current. Contrary to the single hollow cathode chemical vapor deposition, the dual hollow cathode chemical vapor deposition can deposit diamond films free of cathode contaminants, and therefore, enhance the film quality. With the aid of electron bombardment of the substrate, the dual cathode design can grow diamond films of good crystalline quality, and with a high growth rate, 2.3 µ/h, even at a high CH4 concentration such as 10% and at a low pressure of 15 Torr.
Hydrogen Molecule in Group IV Element Crystal
Authors: Nakamura Kazutaka G. , Kunie Ishioka Kunie Ishioka , Masahiro Kitajima Masahiro Kitajima
Published: October 2002

Ab initio Hartree-Fock calculations of a hydrogen molecule in group IV element crystals (diamond, silicon and germanium) have been performed with cluster models. The total energy has a minimum value when the hydrogen molecule is at a tetrahedral site. The charge of the hydrogen molecule in silicon and germanium crystals is neutral but positive in diamond. The calculated vibrational frequencies of H2 are 5533, 4423 and 4402 cm-1 in diamond, silicon and germanium crystals, respectively.
Electroluminescent Devices Based on Poly(diphenylacetylene) with Carbazolyl Side Groups
Authors: Zheng Qianbing , Sun Runguang , Zhang Xianmin , Masuda Toshio , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

By utilizing a newly synthesized paracarbazolyl-substituted poly(diphenylacetylene) (PDPA-Cz) as a hole-transporting layer, high external quantum efficiency was shown to be 2% in electroluminescent devices with a polymer/molecular [PDPA-Cz/tris(8-quinolinolato)aluminum ( Alq3)] heterostructure.
Dielectric Properties of (Ba, Sr)TiO3 Thin Films and their Correlation with Oxygen Vacancy Density
Authors: Fukuda Yukio , Haneda Hajime , Sakaguchi Isao , Numata Ken , Nishimura Katsuhiro Aoki
Published: October 2002

This paper describes the dielectric properties of (Ba, Sr)TiO3 (BST) thin films deposited by rf magnetron sputtering, focusing on their correlation with the oxygen vacancy density in the films. The dielectric properties specific to the BST films can be explained by considering the influence of the dielectric relaxation phenomenon following a power law dependence on time in the time-domain measurement and on frequency in the frequency-domain measurement. From an electrical comparison of the films with and without post-annealing in oxygen ambient, it is derived that charging/discharging electrons at oxygen vacancies in the interfacial Schottky depletion layer, whose width is modulated by the applied voltage, are responsible for the observed dielectric properties. Preliminary results of the oxygen vacancy density measurement using a gas-solid oxygen isotopic exchange reaction showed that the higher the post-annealing temperature, the lower the oxygen vacancy density.
Electric Field-Induced Migration of SiO 2 Particles in Smectic Liquid Crystal
Authors: Tsuyoshi Togo Tsuyoshi Togo , Keizo Nakayama Keizo Nakayama , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The electric field-induced migration of SiO2 particles along a smectic layer has been observed in smectic liquid crystal. SiO2 particles migrate in a sandwiched planer cell of the liquid crystal upon application of an ac electric field. The trace of moved particles is dependent on the alignment of the host liquid crystal molecules. In the phase with a layer structure, such as smectic A and C phases, the particles migrate along the smectic layer, whereas they move in a circular pattern in the isotropic and nematic phases.
Micropatterning Method for the Cathode of the Organic Electroluminescent Device
Authors: Nagayama Kenichi , Yahagi Takashi , Nakada Hitoshi , Watanabe Teruo Tohma Teruichi , Yoshida Kenji , Miyaguchi Satoshi
Published: October 2002

A unique method of micropatterning in the order of microns for an organic electroluminescent (OEL) device has been developed. The method consists of a cathode separator with a reverse tapered or a T-shaped cross section which is formed prior to the deposition of organic layers and metal cathodes. By introducing the cathode separator, a high-resolution OEL display panel with gaps of less than 30 µ m between pixels has been fabricated.
Solid-Phase Reaction of Ni with Amorphous SiGe Thin Film on SiO2
Authors: Jin Zhonghe , Bhat Gururaj A. , Yeung Milton , Hoi S. Kwok Hoi S. Kwok , Man Wong Man Wong
Published: October 2002

A study on the reaction of Ni and amorphous Si0.68Ge0.32 film on SiO2 is reported. The reaction was performed at 520° C in a conventional furnace. The resulting film was characterized using X-ray photoelectron spectroscopy (XPS) and Raman scattering spectroscopy. Ni induced crystallization of SiGe was confirmed by the Raman spectra. XPS results indicate Ni piled up at or near the interface of the crystallized SiGe and the SiO2 substrate. The small amount of Ni inside the SiGe layer exists in more of a silicide- or germanide-like form. Ni enhanced oxidation of SiGe was found during the reaction and the oxidized layer was found to be a mixture of oxides of Si and Ge, with Ge piling up at the surface.
Conducting Polymer-C60 Heterojunctions: Polarity-Independent Electroluminescent Cells
Authors: Zheng Qianbing , Sun Runguang , Zhang Xianmin , Masuda Toshio , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

The characterization of polarity-independent electroluminescent cells based on the heterostructure of a conducting polymer, a soluble para carbazolyl substituted poly(diphenylacetylene) (PDPA-Cz), and buckminsterfullerene, C60, is reported. The operation of the devices under reverse direct-current (dc) bias is discussed in terms of interfacial charge transfer between PDPA-Cz and C60.
Diagnostics of Fluorine Negative Ions by Laser Photodetachment Combined with a Heated Probe in High-Density CF 4 Plasmas
Authors: Noriharu Takada Noriharu Takada , Daiyu Hayashi Daiyu Hayashi , Koichi Sasaki Koichi Sasaki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

This paper reports the absolute density and reaction kinetics of fluorine negative ions (F-) in a low-pressure, high-density CF4 plasma excited by helicon-wave discharge. Probe-assisted laser photodetachment has been adopted for the measurement of the F- density. To avoid the deposition of insulated fluorocarbon films on the probe surface, the probe tip was heated to approximately 1000 K. For a CF4 gas pressure of 2 mTorr, the ratio of the F- density to the electron density was n
-/n
e ≃0.06 in the active discharge plasma with a plasma density of 1.8 ×1012 cm-3. In the afterglow, the electron density decreased rapidly with a decay time constant of ≃10 µs, while the F- density had a peak at ∼15 µs after the termination of the rf power. The ratio n
-/n
e increased up to ∼5.7 in the afterglow. The production and loss processes of F- are discussed based on the experimental observations.
Reduction of Threading Dislocation Density and Suppression of Crack Formation in InxGa 1-xP(x∼0.5) Grown on Si(100) Using Strained Short-Period Superlattices
Authors: Yasufumi Takagi Yasufumi Takagi , Hiroo Yonezu Hiroo Yonezu , Shinobu Uesugi Shinobu Uesugi , Naoki Ohshima Naoki Ohshima
Published: October 2002

We have investigated the reduction of threading dislocations and the suppression of crack formation in In
x
Ga1-x
P (x∼ 0.5) grown on Si using the multi-strained short-period superlattices (SSPSs) by transmission electron microscopy (TEM). The epitaxial layers were grown two-dimensionally and the density of threading dislocations was reduced by the generation of misfit dislocations at all hetero-interfaces. The residual strain was reduced by compensation of the lattice-mismatched stress and the thermal stress, and the formation of cracks was suppressed by controlling the In composition.
Lateral Type Intrinsic Josephson Junctions Using (110) Oriented Grains in Bi2Sr2Ca1Cu2O8+δFilms
Authors: Ishimaru Yoshihiro , Wen Jianguo , Utagawa Tadashi , Naoki Koshizuka Naoki Koshizuka , Youichi Enomoto Youichi Enomoto
Published: October 2002

We have investigated a Josephson junction consisting of an (110) oriented grain surrounded by (001) oriented grains. The Bi2Sr2Ca1Cu2O8+δ(001) oriented films with a few (110) oriented grains are fabricated on MgO(110) substrates by the metalorganic chemical vapor deposition method. TEM observation shows that the grain is (110) oriented of Bi2Sr2Ca1Cu2O8+δand the grain boundary is atomically sharp. HystereticI-Vcharacteristics are observed for the sample with the (110) oriented grain, indicating the presence of the intrinsic Josephson effect caused by stacked CuO2double layers alongc-direction.
Spin-Valve-Like Properties of Ferromagnetic Tunnel Junctions
Authors: Masashige Sato Masashige Sato , Kazuo Kobayashi Kazuo Kobayashi
Published: October 2002

Ferromagnetic tunnel junctions with naturally oxidized Al barriers were fabricated by magnetron sputtering. Using metal masks, 0.01 mm2 junction areas were patterned. Junctions with slightly oxidized Al barriers showed small tunnel resistances. Of those, some had extraordinarily large MR ratios, others had different tunnel resistances according to different current-flow paths, and some had characteristics of both. In contrast, junctions with well oxidized Al barriers exhibited a large tunnel resistance and good stability. The Ni–Fe/Co/Al–AlO

x

/Co/Ni–Fe/Fe–Mn/Ni–Fe junction showed spin-valve-like R-H properties. The MR ratio was 10% for a 20 Oe magnetic field.
Undoped Ga1-xInxSb Grown by Molecular Beam Epitaxy on GaAs Substrates
Authors: H. Roslund Jöran , Gösta Swenson Gösta Swenson , Thorvald G. Andersson Thorvald G. Andersson
Published: October 2002

Growth by molecular beam epitaxy and characterisation of unintentionally doped Ga1-xInxSb layers in the full compositional range on GaAs substrates are reported. The grown samples were characterised by reflection high-energy electron diffraction, X-ray diffraction and Hall-effect measurements. The layers had carrier concentrations below 6 × 1016\kubik with a maximum atx≈0.5, where the conduction switched fromp-type ton-type. Temperature-dependent Hall-effect measurements together with mixed-conduction simulations showed that then-type behaviour is caused by intrinsic electrons and the large electron-hole ratio rather than donor centres.
Fabrication of Perovskite (Pb,La)(Zr,Ti)O 3 Thin Films by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition
Authors: Joong-Shik Shin Joong-Shik Shin , Kwang-Soo No Kwang-Soo No , Won-Jong Lee Won-Jong Lee
Published: October 2002

Lanthanum-modified lead zirconate titanate (PLZT) thin films were fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) using MO sources. The composition of the PLZT films could be controlled by varying the flow rate of each MO source. Perovskite PLZT thin films with a smooth surface and fine grains were successfully fabricated on Pt/Ti/SiO2/Si at 450°C. The deposition mechanism of the PLZT films in the ECR plasma was studied by examining the rate of incorporation of each cation into the film at various MO source flow rates. The microstructure of the deposited films and RTA treatment effects were also evaluated.
High Speed Addressing of a 0°–360° Bistable Twisted Nematic Liquid Crystal Display
Authors: Hoke Charles D. , Li Jianlin , Jack R. Kelly Jack R. Kelly , Philip J. Bos Philip J. Bos
Published: October 2002

In this letter we report the results of an investigation on the dynamics and optics of a twist bistable liquid crystal display. For the first time, the parameters required for high speed addressing of a 0°–360° bistable device are presented. The display consists of a chiral-doped nematic liquid crystal layer with a nominal surface pretilt. The characteristics of the drive waveform allows selection between two optically distinct twist states of 0° and 360°. Optimizing the ratio of cell thickness to inherent pitch and waveform parameters leads to line selection times, for a multiplexed display, of <100 µs; in contrast with typical nematic bistable displays that require times of ∼10 ms. Full optical response can be achieved in times on the order of 15 ms.
Negative Nonlinear Absorption Effect in Erbium Doped Fibers
Authors: Maeda Yoshinobu , Takao Sakakibara Takao Sakakibara , Masatoshi Migitaka Masatoshi Migitaka
Published: October 2002

The dependence of the negative nonlinear absorption effect on both modulation degree and modulation frequency of an incident laser was investigated in erbium-doped fibers at 77 K. Negative input-output characteristics were obtained at modulation frequencies of 10 to 250 kHz for fiber lengths above 2 m. The maximum ratio of the transmitted modulation degree to the incident one was approximately -2 for a fiber length of 4 m. It is suggested that emissions induced in the fiber can contribute to the negative nonlinear absorption effect because they propagate with low loss.
Photoluminescent Intensity from Porous Silicon Depends on Current Density during Anodization
Authors: Masato Ohmukai Masato Ohmukai , Yasuo Tsutsumi Yasuo Tsutsumi
Published: October 2002

We fabricated porous silicon samples under various conditions of current density and anodization time, and investigated the photoluminescent intensity systematically. When anodization time was fixed, positive correlation was observed between current density and photoluminescent intensity. On the other hand, if the total charge transferred during anodization was fixed (in other words, anodization time was inversely proportional to current density), we obtained the maximum photoluminescent intensity at the current density of 20 mA/cm2.
Effect of Alkyl and Aromatic Substituents on Blue Electroluminescence in Polyacetylene Derivatives
Authors: Masaharu Hirohata Masaharu Hirohata , Kazuya Tada Kazuya Tada , Rahmat Hidayat Rahmat Hidayat , Toshio Masuda Toshio Masuda , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Substituent dependences of electroluminescence (EL) and photoluminescence (PL) in disubstituted polyacetylene derivatives such as poly(1-methyl-2-phenylacetylene) (PMePA), poly(1-ethyl-2-phenylacetylene) (PEtPA), poly(1-n-hexyl-2-phenylacetylene) (PHxPA) and poly(1-methyl-2-naphthylacetylene) (PMeNA) have been studied. Blue light emission was observed from EL devices utilizing PEtPA and PHxPA, and blue-green light emission was observed from those utilizing PMePA and PMeNA. EL intensity, relative EL efficiency and PL intensity increase by one or two orders of magnitude on increasing the alkyl chain length. EL intensity, EL efficiency and PL intensity of PMeNA are higher than those of PMePA. The results are discussed in terms of substituent-dependent interchain interaction and electronic energy states.
Self-Generated Magnetic Fields in Laser-Produced Plasmas with 3-D Particle-in-Cell Simulation
Authors: Kazuhito Satou Kazuhito Satou , Toshio Okada Toshio Okada
Published: October 2002

Electron temperature anisotropy has recently been shown through X-ray spectrum experiments and numerical analyses. It is well known that temperature anisotropy causes many kinds of microscopic instabilities, such as self-generation of magnetic fields. There have been many reports about the observation of strong magnetic fields in ultra-intense lasers. It is important to simulate a plasma system using three-dimensional models and methods in order to investigate many types of temperature anisotropy, three-dimensional structures and nonlinear phenomena related to these large-amplitude magnetic fields. In this work, we will demonstrate 3-D particle-in-cell (PIC) simulation and compare the results with recent data.
Au–Ag/Ni/Te Metal Multilayer Contact to p-type ZnSe
Authors: Yoshii Shigeo , Toshiya Yokogawa Toshiya Yokogawa , Yoichi Sasai Yoichi Sasai
Published: October 2002

We report on a new approach for a p-type contact to ZnSe using Au–Ag/Ni/Te multilayer metals which were deposited by resistive heating evaporation and subsequently annealed at 250° C. The current-voltage characteristics were investigated, and a substantial reduction in offset voltage was observed. Cross-sectional high-resolution transmission electron microscopy and electron probe microanalyses revealed the formation of a NiZnSe based amorphous layer between a poly-crystalline NiTe layer and the p-ZnSe. Auger electron spectroscopy indicated the occurrence of interdiffusion at the interface including that of Ag atoms. The reduction in the offset voltage is attributed to the presence of the amorphous interlayer and the heavily Ag doped layer at the contact interface.
Enhanced Phase Modulation by Cascaded Second-Order Effects in Quasi-Collinear Configuration
Authors: Lei Zhang Lei Zhang , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

An approximate expression of the nonlinear phase modulation induced by cascaded second-order effects has been derived for both the collinear and quasi-collinear second-harmonic generations in the limit of small fundamental depletion. In the quasi-collinear case, the nonlinear phase shift in one fundamental beam consists of a self-phase modulation proportional to its intensity and an induced phase modulation which is twice as large as the self-phase modulation in the other beam.
Effect of H2 Annealing on a Pt/PbZrxTi1-xO3 Interface Studied by X-Ray Photoelectron Spectroscopy
Authors: Takatani Shinichiro , Keiko Kushida-Abdelghafar Keiko Kushida-Abdelghafar , Hiroshi Miki Hiroshi Miki
Published: October 2002

The chemical reaction and the change in the Schottky barrier height at the Pt/PbZr

x

Ti1-
x

O3 (PZT) interface as a result of annealing was studied by in-vacuo X-ray photoelectron spectroscopy. Annealing at 320° C produced metallic Pb atoms which migrated on the Pt surface. There were more of these atoms when the annealing was done in H2 than in a vacuum. After H2 annealing, the core level peaks for the elements in the PZT showed a band bending shift of ∼0.4 V toward higher binding energy, indicating that the n-type Schottky barrier height at the Pt/PZT interface was lowered by the H2 annealing.
Correlation between the Photochromic Enhancement in Tungstic Acid and the O-C-H Bond in Additives
Authors: Keiichi Kuboyama Keiichi Kuboyama , Kazuhiro Hara Kazuhiro Hara , Kazumi Matsushige Kazumi Matsushige , Shoichi Kai Shoichi Kai
Published: October 2002

Photochromism of tungstic acid is remarkably improved by addition of a specific additive. In this study, it was found that the photochromic enhancement is independent of the polymerization degree of the additive polyethylene glycol. Based on this result, we reexamined the enhancement using various organic additives which contain bonds such as O-H and O-C-H in their chemical structures. Then, it was determined that the O-C-H structure plays an essential role for the enhancement. A more sophisticated explanation is proposed for the photochromic enhancement by the organic additives.
Fast Electrons from Grimm Glow Discharge Helium Plasmas
Authors: Tsuji Kouichi , Hideyuki Matsuta Hideyuki Matsuta , Kazuaki Wagatsuma Kazuaki Wagatsuma
Published: October 2002

Pulsed high voltages with a maximum of 5 kV were applied to the Grimm glow discharge lamp using helium gas. Strong radiation of the continuous X-rays and the characteristic X-rays from the window materials of Al and Zr thin films was observed. We consider that the high-energy electron, namely, the runaway electron, emitted from the cathode surface passed right through the hollow anode and bombarded the X-ray window, resulting in the X-ray emission. This electric discharge lamp is expected to be useful as a new electron and soft-X-ray source.
Improvement of a-Si:H Solar Cell Characteristics by means of a Boron-Carbon Window Layer
Authors: Matsumoto Yasuhiro , Asomoza Rene , Merkulov Alexander , Hirata Gustavo , Cota-Araiza Leonel
Published: October 2002

Thin film p-i-n-type hydrogenated amorphous silicon solar cells have been obtained using the conventional technique of plasma-enhanced chemical vapor deposition employing only boron and carbon as a “p”-layer window. This layer was obtained using the common gas sources CH4 and B2H6 (methane and diborane) and has properties similar to those of a p-type semiconductor such as a-Si:C (amorphous silicon carbide). Auger electron spectroscopy and secondary ion mass spectroscopy were employed to verify the boron carbon deposition on single-crystalline silicon. Solar cells with a total thickness of only 300 nm have a short-circuit current density of 13.3 mA/cm2 with an open-circuit voltage of 870 mV. The efficiency of the solar cells was considerably increased when the B-C window layer was applied.
Sedimentation of Atoms in Solid under a Strong Acceleration Field of around 1 Million g
Authors: Mashimo Tsutomu , Satoru Okazaki Satoru Okazaki , Suguru Tashiro Suguru Tashiro
Published: October 2002

The behavior of atoms in a solid under a strong acceleration field of around 1 million (106) g at high temperature (mega-gravity field) was examined. The ultracentrifuge experiment was performed on an antimony (Sb)-bismuth (Bi) system solid alloy in a maximum acceleration field of (0.85–1.03)×106 g at 220–240° C for 85 hours. Large composition gradients of Sb (about 20–0 wt%) and Bi (80–100 wt%) and the continuous changes in lattice parameters were observed at that location where the external energy was comparable to or larger than the thermal energy. This result provides the first evidence of the sedimentation of component atoms in a solid.
Narrow-Channel Metal Oxide Semiconductor Field Effect Transistor (MOSFET) Isolated by an Ultra-Fine Trench
Authors: Oishi Toshiyuki , Shiozawa Katsuomi , Furukawa Akihiko , Yuji Abe Yuji Abe , Yasunori Tokuda Yasunori Tokuda
Published: October 2002

We show an advanced fabrication process for trench isolation to produce metal oxide semiconductor field effect transistors (MOSFETs) with sufficient electrical properties in a very narrow active region. This process, in which we added an oxide spacer formation step, drastically improved the edge configuration of the trench isolation, where the reduction of the effective channel width of the MOSFET is as small as 0.05 µ m. The threshold voltage of the MOSFET isolated by this trench scarcely decreased down to the channel width of 0.21 µ m, while the subthreshold characteristics have no kink even without sidewall implantation which suppresses the concentration of the electric field at the channel edges.
In Situ Photoluminescence Analysis of Nonradiative Recombination on Silicon Surfaces Treated in Fluoride Solution
Authors: Timoshenko Victor Yurievich , Rappich Jörg , Dittrich Thomas
Published: October 2002

Recombination at p-type Si(100) surfaces electrochemically treated in NH4F solution is investigated in situ by photoluminescence (PL) under excitation with short pulses of a N2-laser. By registration of the integrated PL intensity we detect sensitively changes in the surface defect concentration. Periodic variations of the nonradiative recombination rate during electropolishing in the oscillating regime together with surface passivation by hydrogenation are observed. The estimated density of the surface nonradiative centers changes from 1013 cm-2 during the electropolishing to 5×1010 cm-2 for quiescent hydrogenated surfaces.
Cross-Polarization Scattering from Low-Frequency Waves in a Tandem Mirror Plasma
Authors: Kogi Yuichiro , Mase Atsushi , Bruskin Leonid G. , Oyama Naoyuki , Tokuzawa Tokihiko , Itakura Akiyosi , Hitoshi Hojo Hitoshi Hojo , Teruo Tamano Teruo Tamano
Published: October 2002

Cross-polarization scattering (CPS) diagnostic was applied to the central-cell plasma of the GAMMA 10 tandem mirror in order to study electromagnetic plasma waves with frequencies of less than 200 kHz. In the CPS process, an incident ordinary (extraordinary) wave is converted to an extraordinary (ordinary) wave by magnetic fluctuations in a plasma. The converted wave propagates through the cutoff layer and reaches the opposite diagnostic port. The experimental data suggest that the power spectral density of the CPS signal satisfies the Bragg condition, while the reflectometer detects the waves near the cutoff layer where the wave number cannot be resolved.
Observation of Color Image Using Near-Field Optical Microscope
Authors: Masashi Kiguchi Masashi Kiguchi , Midori Kato Midori Kato , Masayoshi Ishibashi Masayoshi Ishibashi
Published: October 2002

A color image was observed using a near-field optical microscope with a He-Cd laser that lases in three primary colors. A Cu-phthalocyanine film was perceived to be blue in the image, and its actual color was almost exactly reproduced in the image. Additionally, a white particle speculated to be a dust particle was observed in the image and discerned from the film by color. The microscopically measured transmittance for each color agreed well with the spectrum macroscopically measured by a conventional spectrometer.
Polarization-Tunable X-Ray Optics for Synchrotron Radiation
Authors: Keiichi Hirano Keiichi Hirano
Published: October 2002

A new type of polarization-tunable X-ray optics for synchrotron radiation is proposed. The optics consists of a double-crystal monochromator and a transmission-type phase plate. The monochromator and the phase plate are arranged in a (+, -) parallel setting, and their scattering plane is inclined by α° (α≠0°, 90°) from the horizontal plane. The optics were tested on beamline BL-15C of the Photon Factory; circular and vertical polarizations were successfully produced at a wavelength of 0.1026 nm. The polarization transformation efficiency at the phase plate was as high as 70%.
Effects of Antimony Diffusion into Porous Silicon Light Emitting Diodes
Authors: Nishimura Kohsuke , Yasuyuki Nagao Yasuyuki Nagao , Noriaki Ikeda Noriaki Ikeda
Published: October 2002

Porous silicon (PS) light emitting diodes (LEDs) consisting of n-PS/p-PS/p-Si or n-PS/p-Si structures fabricated by postanodical Sb diffusion were characterized for assessment of the effect of Sb diffusion upon PS-LED characteristics. The homogeneity of electrical characteristics of PS-LEDs was improved by Sb diffusion. Consequently, the average series resistance of the Sb-diffused PS-LEDs was found to be lower than that of nondiffused PS-LEDs. The average external quantum efficiency of the PS-LEDs was also enhanced by Sb diffusion. The experimental results were discussed.
InGaP/InGaAs/GaAs High Electron Mobility Transistor Structure Grown by Solid Source Molecular Beam Epitaxy Using GaP as Phosphorous Source
Authors: Missous Mohamed , Sandhu Azlan Abdul Aziz
Published: October 2002

InGaP/InGaAs/GaAs pseudomorphic high electron mobility transistor (HEMT) structures were grown on 3-inch GaAs (100) substrates by solid source molecular beam epitaxy using polycrystalline GaP as a phosphorous source. The inclusion of a 5 nm thick AlGaAs layer between the InGaP and InGaAs yielded the best electrical characteristics, where the room temperature mobility and sheet carrier concentration were 5200 cm2/V·s and 1.8×1012 cm-2, respectively. A 5×100 µ m2 HEMT device fabricated using this structure yielded an extrinsic transconductance of 80 mS/mm.
Electrical Drift Phenomenon due to Deep Donor Defects Induced by Reactive Ion Etching (RIE) Using Mixture of Ethane (C2H6) and Hydrogen (H2)
Authors: Yamamoto Norio , Kishi Kenji , Matsumoto Shin-ichi , Kadota Yoshiaki , Hiroshi Okamoto Hiroshi Okamoto , Hiroyasu Mawatari Hiroyasu Mawatari
Published: October 2002

The electrical properties of an InP surface treated with a process involving reactive ion etching (RIE) with a mixture of ethane ( C2H6) and hydrogen ( H2) were studied. For the treated surface, an electrical drift phenomenon was observed: Schottky barrier height φ increased under a forward bias condition. On the other hand, the drift was not observed under a reverse bias condition. The drifted φ returned to its initial value when the surface was left at RT after removing the bias. The drift is considered to be caused by a change of the electrical charge of deep donor defects induced by the RIE.
All-Optical Switching Dynamic Interconnection with Multiple Mutually Pumped Phase Conjugators
Authors: Yujin Zheng Yujin Zheng , Akira Sasaki Akira Sasaki
Published: October 2002

An all-optical controllable dynamic interconnection and an all-optical switching dynamic interconnection are demonstrated using the arrangements of the multiple mutually pumped phase conjugators in a photorefractive Cu-doped (K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 [Cu:KNSBN] crystal. The ON and OFF states of dynamic interconnection between the two light beams were dominated by a control beam. The dynamic interconnections of the multiple light beams were also optically switched via the incidence of the different control beams.