bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Properties of Perfluoroalkylated Poly(diphenylacetylene)
Authors: Tada Kazuya , Sawada Hideo , Kyokane Jun , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Optical properties of a soluble conducting polymer, perfluoroalkylated poly(diphenylacetylene) (PFPDPA) were clarified. The band-gap energy was evaluated to be about 2.7 eV.
Relatively strong fluorescence was observed in PFPDPA, while poly(diphenylacetylene) (PDPA) is considered to be a conducting polymer with a degenerated ground state in which a soliton is considered to play an important role. A light-emitting diode (LED) with In-Mg/PFPDPA/indium-tin-oxide (ITO) configuration was fabricated and green light emission was observed.
Adhesion of Resist Micropatterns during Drying after Water Rinse
Authors: Akira Kawai Akira Kawai
Published: October 2002

The variation of residual strain in photoresist thin films can be detected by a strain gauge with high sensitivity. The adhesion of resist micropattern during drying after water rinse is studied in terms of the residual strain variation. The residual strain of a resist film varies markedly as water is evaporated from the resist surface. In order to improve the resist adhesion, it is important to decrease the residual strain during the drying process.
Ion Influence on Nematic Liquid Crystal Cell Impedance at Low Frequency
Authors: Mada Hitoshi , Masahiro Ryuzaki Masahiro Ryuzaki
Published: October 2002

Electric impedance of nematic liquid crystal (5CB) cells has been measured to detect ion behavior. The experimental and theoretical results show that a single type of ion carries a current in 5CB.
The thickness of double layer at the surface becomes thinner with decrease in the frequency.
Fabrication of 10-Nanometer-scale GaAs Dot Structures by In Situ Selective Gas Etching with Self-Assembled InAs Dots as a Mask
Authors: Go Yusa Go Yusa , Hiroshi Noge Hiroshi Noge , Yutaka Kadoya Yutaka Kadoya , Takao Someya Takao Someya , Tadatomo Suga Tadatomo Suga , Pierre Petroff Pierre Petroff , Hiroyuki Sakaki Hiroyuki Sakaki
Published: October 2002

We report on a novel method of fabricating 10-nm-scale GaAs dot structures using molecular beam epitaxy and in situ gas etching. Self-assembled nanometer-scale InAs dots are formed first and are used as masks for the subsequent etching of GaAs by Cl2 gas. In this approach, we also make use of HCl gas etching to remove selectively the InAs wetting layer as well as the InAs dots to yield clean and strain-free GaAs dot structures. The height and base diameter of resultant GaAs dots are studied by atomic force microscopy and found to be 10±2 nm and 30±5 nm, respectively.
Microwave-Induced dc Voltages in BaPb1-xBixO3 Bicrystal Josephson Junctions
Authors: Fuke Hiroyuki , Hayashi Kunihiko , Kanke Yukio , Youichi Enomoto Youichi Enomoto
Published: October 2002

We have fabricated an artificial BaPb1-
x

Bi

x

O3 grain boundary tunnel junction on a SrTiO3 bicrystal substrate. Current-voltage characteristics exhibit supercurrent and quasi-particle tunneling which is commonly observed for superconductor-insulator-superconductor (SIS) type junctions. A Shapiro step is observed for a junction with a large area under microwave radiation. On the other hand, microwave-induced dc voltages at zero bias current are observed for a narrow junction. This dependence on the junction width indicates that generation of the microwave-induced voltages is related to normal resistance or capacitance of a junction.
Persistent Photoconductivity in C60-Doped Poly(3-alkylthiophene)
Authors: Yoshino Katsumi , Akashi Tatsuo , Yoshimoto Kenji , Morita Shigenori , Kawai Tsuyoshi , Zakhidov Anvar A.
Published: October 2002

Persistent photoconductivity (PPC) has been observed in C60-doped poly(3-alkylthiophene) (PAT). PPC increases with increasing irradiation time, tending toward saturation. PPC also increases with C60 concentration, tending toward saturation or even decrease at high concentration. Novel temperature dependence of PPC has been observed. This PPC has been discussed in terms of enhanced photoexcited carrier density in C60 doped PAT and the suppression of the recombination of primary negative and positive carriers due to the stabilization of trapped electrons in C60 and defect states in PAT.
Ultraviolet Electroluminescent Diode Utilizing Poly(methylphenylsilane)
Authors: Akihiko Fujii Akihiko Fujii , Kenji Yoshimoto Kenji Yoshimoto , Masayoshi Yoshida Masayoshi Yoshida , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electroluminescent (EL) diode utilizing poly(methylphenylsilane) (PMPS) has been fabricated and its optical and electroluminescent characteristics have been investigated. We have succeeded in demonstrating ultraviolet emission at 353 nm from the PMPS EL diode for the first time.
Compensated-Strain Multiquantum-Well Active Layer for InGaAlP-Based Visible Light Emitting Diodes
Authors: Sugawara Hideto , Masayuki Ishikawa Masayuki Ishikawa
Published: October 2002

Compensated-strain multiquantum-well (CS-MQW) structures have been investigated as the active region for InGaAlP-based visible light emitting diodes (LEDs). Strained layers for the LED active region were successfully grown by metalorganic chemical vapor deposition (MOCVD) with a compensated-strain structure. The total thickness of the strained active region was six times thicker than the critical thickness of the single strained layer. The precise control of a 20-quantum-well structure with tensile-strained wells and compressive-strained barriers was confirmed by X-ray diffraction measurements. A high-efficiency short-wavelength (585 nm) light emission was obtained for a current injection LED with the CS-MQW active region.
Efficient Stimulated Raman Scattering in Tetragonal Laser Crystalline Hosts NaBi(MoO 4) 2 and NaBi(WO 4) 2
Authors: A. Kaminskii Alexander , N. Bagayev Sergey , Ken-ichi Ueda Ken-ichi Ueda , Hajime Nishioka Hajime Nishioka , Yoshinori Kubota Yoshinori Kubota , Xu Chen Xu Chen , Akhmed Kholov Akhmed Kholov
Published: October 2002

The efficient Raman scattering in two tetragonal laser crystalline hosts with disordered structure has been studied by Q-switched infrared laser pulse excitation. Raman spectra show that such disordered crystals have larger cross sections than those of typical ordered crystals. The effective Raman gain coefficients were estimated as (9±4) cm/GW for NaBi(MoO4)2 (across c-axis) and as (8±4) cm/GW for NaBi(WO4)2.
Dissociative Ion Yields on Metal Surfaces Bombarded with Low-Energy Fluorocarbon Ions
Authors: Mitsuoka Yoshihito , Toyoda Hirotaka , Sugai Hideo
Published: October 2002

Fluorocarbon ions ( CF+
3, CF+
2 and CF+) are mass-selected from a CF4 plasma and irradiated onto aluminum surfaces at energies up to 140 eV, to investigate the surface processes relevant to reactive ion etching. The irradiation of a CF+

x

beam (x=1-3) at impact energies higher than 50-100 eV yields the smaller fragment species CF+

y

(y<x) on the surface, in addition to the reflected species (y=x). The energy distribution function of each ion species scattered from the surfaces has been measured for the first time; most of the ions have kinetic energies lower than 10 eV while some reflected species have energies comparable to the incidence energy. In contrast to the previous results of hydrocarbon ions ( CH+

x

), the low-energy incidence (<50 eV) of fluorocarbon ions gives a low scatter of ions from the surface, except for the case of CF+
3 incidence. The possible mechanisms of dissociation of fluorocarbon ions as a result of ion-surface interactions are discussed.
Cross-Polarization Scattering from Electromagnetic Plasma Waves in Ion Cyclotron Range of Frequencies
Authors: Mase Atsushi , Bruskin Leonid G. , Kobayashi Masashi , Oyama Naoyuki , Tokuzawa Tokihiko , Itakura Akiyosi , Hojo Hitoshi , Ichimura Makoto , Teruo Tamano Teruo Tamano
Published: October 2002

The cross-polarization scattering diagnostic system is applied to the central-cell plasma of the GAMMA 10 tandem mirror in the study of electromagnetic plasma waves in the ion cyclotron range of frequencies. An incident ordinary (extraordinary) wave is converted to an extraordinary (ordinary) wave by magnetic fluctuations. The converted wave can propagate through the cutoff layer and reach the detector. The transmitted and reflected waves are investigated at various incident frequencies. The experimental data suggest that density and magnetic fluctuations of similar levels are excited in a plasma due to the instabilities in the ion cyclotron range of frequencies.
Discriminative Imaging of Local Crystalline Density and Thickness Variation in Strained Natural Rubber by Spectroscopic X-Ray Scattering Topography
Authors: Suzuki Yoshifumi , Chikaura Yoshinori , Udagawa Yoshitaka
Published: October 2002

X-ray spectroscopic scattering topography using an energy dispersive solid state detector has been applied to discriminate a local crystallization effect from the influence of thickness variation in strained natural rubber. ZnKα X-rays which are emitted from the zinc oxide additive are selected in the multichannel spectra to provide a thickness distribution map in the specimen. With appropriate calibration we could measure the distribution of thickness quantitatively, while X-rays with a longer wavelength than ZnKα are employed to form the X-ray topograph indicating the degree of crystallization.
Annealing Energy Distribution of Light-Induced Defects of Hydrogenated Amorphous Silicon Films Grown from Silane and Dichlorosilane Gas Mixtures
Authors: Osborne Ian S. , Hata Nobuhiro , Akihisa Matsuda Akihisa Matsuda
Published: October 2002

The distributions of annealing energies of light-induced defects obtained from a study of the defect annealing kinetics of films grown from silane and dichlorosilane gas mixtures by plasma enhanced chemical vapour deposition are reported. The results are modelled using a gaussian distribution of annealing energies. The addition of dichlorosilane is found to affect the magnitude and position of the defect annealing energy distribution. As measured by the constant photocurrent method, these films show an increased stability to the creation of light-induced defects under intense pulsed laser illumination.
Semispiral Structure of Turbostratic Boron Nitride Formed under High Pressure and High Temperature
Authors: Horiuchi Shigeo , Lian-Long He Lian-Long He , Minoru Akaishi Minoru Akaishi
Published: October 2002

Fine structures appearing in a hexagonal boron nitride (h-BN) under high pressure (7.7 GPa) and high temperature (1800° C) are examined by high-resolution transmission electron microscopy. At the edge of plate-like h-BN crystal sp2 sheets are strongly bent to form a semispiral structure of t (turbostratic)-BN with an average interplaner spacing of 3.5 Å; edges of h-BN plates are covered by the curved sp2 sheets so that dangling bonds are minimized. This occurs when the edges of a group of h-BN plates comes up to the planes of another group. The similar structure occurs also inside the crystal near the plate edge. The origin of the semispiral t-BN is discussed from the viewpoint of chemical bonding.
Enhanced Microlithography Using Combined Phase Shifting and Off-axis Illumination
Authors: Erdélyi Miklós , Bor Zsolt , Cavallaro Joseph R. , Szabó Gabor , Wilson William L. , Sengupta Chaitali , Smayling Michael C. , Frank K. Tittel Frank K. Tittel
Published: October 2002

Off-axis illumination is a promising optical microlithography technique which can be used to improve the image quality of line-space patterns. With this method the image is produced by the zero and first order diffracted beams. Due to the intensity difference between these two order diffracted beams the contrast of the image cannot be unity. This paper demonstrates the optical enhancement that can be achieved by a combination of interferometric phase shifting and off-axis illumination. In such an arrangement the mask is illuminated symmetrically from both the front and back sides, and not two but in fact four–(two zero and two first)–order beams produce the image. We show experimentally that the contrast of the image can be improved if the phase difference between the reflected and transmitted beams is π, and the intensity of the transmitted beam is about 13% of the reflected beam. This improved quality image with feature sizes of 0.4 µm was recorded in a photoresist using an Ar+ ion laser operating at 457.9 nm.
Fabrication and Microwave Responses of YBa2Cu3O7-x Superconducting Thin-Film Nanobridges
Authors: Lu Wu , Shen Hao-Ying , Gu Ning , Lee Jin-Hee , Wei Chul-Soon Park
Published: October 2002

Superconducting nanobridges with a width smaller than 150 nm were patterned by electron beam/ultraviolet (EB/UV) hybrid exposure technique in YBa2Cu3O7-
x

(YBCO) thin films. There was no significant decrease in transition temperature and critical current density compared with unstructured films. For a 120-nm-wide nanobridge, as high as 150 µA critical current was obtained at 77 K.
High-Rate Anisotropic Ablation and Deposition of Polytetrafluoroethylene Using Synchrotron Radiation Process
Authors: Inayoshi Muneto , Ikeda Masanobu , Hori Masaru , Goto Toshio , Hiramatsu Mineo , Hiraya Atsunari
Published: October 2002

Both anisotropic ablation and thin film formation of polytetrafluoroethylene (PTFE) were successfully demonstrated using synchrotron radiation (SR) irradiation of PTFE, that is, the SR ablation process. Anisotropic ablation by the SR irradiation was performed at an extremely high rate of 3500 µm/min at a PTFE target temperature of 200° C. Moreover, a PTFE thin film was formed at a high rate of 2.6 µm/min using SR ablation of PTFE. The chemical structure of the deposited film was similar to that of the PTFE target as determined from Fourier transform infrared absorption spectroscopy (FT-IR) analysis.
Blue Electroluminescent SrGa2S4:Ce Thin Films Grown by Molecular Beam Epitaxy
Authors: Inoue Yoji , Tanaka Katsu , Okamoto Shinji , Kobayashi Kikuo , Isao Fujimoto Isao Fujimoto
Published: October 2002

SrGa2S4:Ce thin films have been grown by molecular beam epitaxy, using the source materials of Sr metal and Ga2S3. Polycrystalline films are obtained at a growth temperature of 560° C without annealing and their chemical composition ratio of Sr:Ga:S is 1:1.94:3.94. The SrGa2S4:Ce films show pure blue photoluminescence and electroluminescence with the CIE color coordinates of x=0.14 and y=0.13.
Superconductivity in Artificially Layered (BaAuOx)(BaCuO2+y)(CaCuO 2) 2 Thin Films
Authors: Matunari Shuuiti , Kanai Masaki , Tomoji Kawai Tomoji Kawai
Published: October 2002

Thin films of (BaAuO

x

)(BaCuO2+
y

)(CaCuO2)2 artificial lattices have been grown by the atomic layer-by-layer growth technique with laser molecular beam epitaxy. These materials have a similar crystal structure to CuBa2Ca2Cu3O

x

where the Cu site between adjacent BaO layers is replaced by Au. This site-selective substitution brings about a change in the relative intensities of X-ray diffraction pattern peaks and increases the lattice constant c from 1.51 nm to 1.57 nm. This Au-based cuprate film shows zero resistance at 20 K with the onset temperature of 60 K.
High-Reflectivity In0.29Ga0.71As/In0.28Al0.72As Ternary Mirrors for 1.3 µm Vertical-Cavity Surface-Emitting Lasers Grown on GaAs
Authors: Otsubo Koji , Shoji Hajime , Fujii Takuya , Matsuda Manabu , Hiroshi Ishikawa Hiroshi Ishikawa
Published: October 2002

High-reflectivity In0.29Ga0.71As/In0.28Al0.72As ternary mirrors have been designed and fabricated on GaAs substrates with InGaAs graded buffer layers for 1.3 µ m vertical-cavity surface-emitting lasers (VCSELs). Theoretical calculation predicts that a 10-pair In0.29Ga0.71As/In0.28Al0.72As mirror can achieve higher peak reflectivity and wider stop bandwidth than a 20-pair InP/InGaAsP one. The ternary mirrors grown by metalorganic vapor phase epitaxy (MOVPE) exhibit high reflectivity, and measured characteristics show good agreement with the designed performance.
A Passively Q-Switched Nd:YAG Laser with a Variable Pulse Width Using LiF:F2
- Color-Center Crystal in a Dual-Cavity Configuration
Authors: Kim Nam Seong , Hong Jin Kong Hong Jin Kong
Published: October 2002

We report a Q-switched Nd:YAG laser using a dual-cavity configuration which enables the pulse width to be varied between 24 ns and 32 ns. We used a LiF:F2
- color-center crystal for passive Q-switching and an auxiliary cavity for lasing the emitted light from the LiF:F2
- crystal. The lasing in the auxiliary cavity causes the LiF:F2
- to reclose and a tail of the Q-switched pulse to be cut out. The rate equations were used to investigate the output characteristics from a Q-switched laser with a dual-cavity configuration. The experimental results were in good agreement with the results of the theoretical simulation.
In-Line Fiber Grating-Type Optical Bandpass Filter Tuned by Applying Lateral Stress
Authors: Komukai Tetsuro , Miyajima Yoshiaki , Masataka Nakazawa Masataka Nakazawa
Published: October 2002

An in-line tunable optical bandpass filter consisting of an optical circulator and a fiber grating has been demonstrated by applying lateral stress to the grating. The center wavelength can be tuned over 8 nm (2 nm shorter and 6 nm longer). The shift rate is estimated to be 1.26 nm per Newton at around 1.55 µ m for a dispersion shifted fiber, which results in a measured Young's modulus of 9.97×1010 N/m2.
Formation and Surface Acoustic Wave Properties of LiNbO3/AlN/Sapphire
Authors: Shibata Yoshihiko , Kanno Yasuhito , Kaya Kiyoshi , Kanai Masaki , Kawai Tomoji
Published: October 2002

Thin films of LiNbO3 have been formed on AlN films (AlN/sapphire) by pulsed laser deposition. The epitaxial growth of LiNbO3 films is confirmed by X-ray pole figure analysis. Theoretical calculation of surface acoustic wave (SAW) properties has been performed for LiNbO3/AlN/sapphire. Preliminary results of experimental SAW properties have been shown.
Excess Current through Single-Barrier Structures with Si-planar-doped AlAs Layer
Authors: Hiroyuki Fukuyama Hiroyuki Fukuyama , Takao Waho Takao Waho
Published: October 2002

We study tunneling current through single-barrier structures with a Si-planar-doped AlAs barrier layer inserted between GaAs layers. We find excess current that is not observed when the AlAs barrier is undoped. The derivative of the current-voltage characteristics indicates that this excess current flows through zero-dimensional states. The excess current probably results from resonant tunneling through Si-impurity states formed in the AlAs single barrier.
Novel Photomemory Effects in an Amorphous Photochromic Dye
Authors: Koshido Takashi , Kawai Tsuyoshi , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The stable amorphous state of a photochromic dye, cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene, has been prepared and its optical and electrical properties have been studied. In this stable amorphous dye, changes of the optical and electrical properties upon photoisomerization are found, with which novel photomemory effects have been realized.
Real-Time Observations on the Cleaning Process of Patterned GaAs Substrates
Authors: Morishita Yoshitaka , Nomura Yasuhiko , Goto Shigeo , Yamada Masamichi , Yoshifumi Katayama Yoshifumi Katayama
Published: October 2002

We report on real-time scanning microprobe reflection high-energy electron diffraction (µ-RHEED) observations on the cleaning process of mesa-etched GaAs (100) surfaces for the first time. Both the initial (100) surfaces and the (111)A sidewall have been found to be uniformly cleaned at temperatures of about 400° C using atomic hydrogen ( H•); further, RHEED intensity oscillations more than 50 periods have been observed during direct molecular-beam epitaxy (without a GaAs buffer layer) of GaAs on the cleaned (100) surface. On the other hand, an inhomogeneous desorption of the oxide layer has been observed during conventional thermal cleaning under an As4 pressure at about 600° C. The results indicate that the H• treatment of patterned substrates is useful for obtaining smooth and clean surfaces without the growth of a GaAs buffer layer.
Spontaneous Motion of Amphoteric Polymer Gels on Water
Authors: Osada Yoshihito , Gong JianPing , Uchida Makoto , Noriharu Isogai Noriharu Isogai
Published: October 2002

We have discovered that cross-linked hydrophobic-hydrophilic copolymer gels swollen in organic solvent undergo spontaneous motion when immersed in water. The mode of motion largely depends on the shape of the gel: a disc-shaped gel exhibits translational motion while a triangular or a square shaped one exhibits rotation. The velocity and duration of gel motion are strongly associated with its size and chemical structure. We consider that the gel, immersed in water, rapidly forms a partially organized structure on its outer surface and gradually shrinks, simultaneously producing high osmotic pressure and hydrostatic pressure. By virtue of these two pressures, the organic solvent is released from the gel and the gel obtains a net reaction force to induce motion, presumably due to its heterogeneous structure.
Intense-Electron-Beam Transportation through an Insulator Beam Guide
Authors: Musuhi Hakoda Shinichi Nishiyama , \) \)
Published: October 2002

The purpose of our research is to elucidate the role of plasma located at the insulator surface in intense-electron-beam transportation. Positive ions are extracted from the plasma by the electron beam space charge. The ion extraction is self-regulated by the net space charge of the electron beam. The ions expand over the transport area, and the beam charge is neutralized effectively by the ions. Consequently, the electron beam propagates efficiently through the insulator beam guide. In our study, we discuss the transportation of the intense electron beam based on results of a computer simulation.
Spectroscopic Ellipsometry Studies on Optical Constants of Ge2Sb2Te5 Used for Phase Change Optical Disks
Authors: Ide Tatsunori , Suzuki Michio , Mitsuya Okada Mitsuya Okada
Published: October 2002

Spectroscopic ellipsometry has been applied to Ge2Sb2Te5, which is commonly used as a recording layer for phase change optical disks, and the optical constants have been measured for a wavelength range from 400 to 900 nm. We have improved the accuracy of this measurement by means of inserting a transparent film between a Ge2Sb2Te5 film and a Si substrate. A calculation of the reflectivity change, due to the phase transition between the amorphous and the crystalline states, shows that the change is sufficient for optical optimization of the disk structure, down to the 400 nm wavelength.
Fabrication of Superconducting Hg-1223 Filament by Solution Spinning Method
Authors: Tomoko Goto Tomoko Goto
Published: October 2002

The fabrication of Hg1223 filament was studied through solution spinning method by partial-substituting Sr for the Ba site and Re addition. The precursor (Ba0.8Sr0.2)2Ca2Cu3Re1O

x

filament with diameter of 250 µ m was reacted in a controlled Hg atmosphere. The filament was nearly single phase of Hg1Ba2Ca2Cu3O

x

(Hg1223) with
T
c
of 127 K.
The maximum transport critical current density (
J
c
) of the filament at 77 K and 0 T was attained to 1000 A/cm2. The plane-like grains were packed densely in the filament. The effect of oxygen annealing of the filaments was minor.
Surface Resistance Measurement on YBCO Thin Film and Bulk Plate by a Modified Parallel-Plate Resonator Method
Authors: Kim In-Seon , Lee Kyu Won , Park Yong Ki , Jong-Chul Park Jong-Chul Park
Published: October 2002

Parallel-plate resonators have been used to measure the surface resistance R
s of YBCO( YBa2Cu3O7-δ) thin films and bulk plates at X-band microwave frequency. A new simple coupling configuration which comprises a parallel-plate resonator inserted into a waveguide was adopted for the measurement. The surface resistance measurement on Au thin film showed good agreement with the calculated value. We measured the surface resistance on the YBCO parallel-plate resonators using both thin films and bulk plates in the temperature range from 50 K to 300 K.
In the case of the YBCO thin films deposited on LaAlO3 substrate, we obtained R
s values of 0.013 and 0.24 Ω at 77 and 300 K, respectively.
Spatial Frequency Doubling Method for Sub-0.15-µm Optical Lithography
Authors: Otaka Akihiro , Kawai Yoshio , Tanaka Akinobu , Tadahito Matsuda Tadahito Matsuda
Published: October 2002

A new method for fabricating fine periodic patterns with a large depth of focus is proposed. It is based on flattening the 1st-order intensity distribution at the image plane and extracting the 2nd-order intensity distribution which has double the spatial frequency of the mask pattern. The resolution is improved up to the incoherent cutoff frequency (2
N
A
/λ) and the image can be created independently of the defocus and the pattern direction. This method is achieved by superimposing optical images with two focal planes under coherent illumination. Using this method, a 0.14-µ m lines and spaces pattern can be fabricated by KrF lithography with a large depth of focus of 2.0 µ m.
New Magnetic Phases in the R-Cu-O (R=Tm and Y) Systems
Authors: Tatsuki Tadashi , Adachi Seiji , Itoh Makoto , Tamura Toshiyuki , Wu Xiao-Jing , Jin Chang-Qing , Yamauchi H. , Koshizuka Naoki , Shoji Tanaka Shoji Tanaka
Published: October 2002

Ferromagnetic-like transitions have been observed for R-Cu-O ( R= Tm and Y) samples heat-treated at 1000° C under a high pressure of 5 GPa. The transition occurs at ∼30 K for both Tm-Cu-O and Y-Cu-O.
Nearly single-phase samples were prepared for a cation ratio of Tm/Cu=1.0/1.8. This phase has monoclinic I2/a symmetry with the lattice parameters a=5.660(1) Å, b=9.544(2) Å, c=5.582(2) Å and β=92.52(1)°. Compositional analyses revealed that the ratio of the two cations was Tm/Cu=1.00/1.87, i.e. not exactly equal to 1/2.
Polarization Anisotropy of Organic Electroluminescent Diode with Periodic Multilayer Structure Utilizing 8-Hydroxyquinoline Aluminum and Aromatic Diamine
Authors: Fujii Akihiko , Yoshida Masayoshi , Ohmori Yutaka , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

An electroluminescent diode with periodic multilayer structure consisting of alternating layers of 8-hydroxyquinoline aluminum and aromatic diamine has been fabricated by organic molecular beam deposition. Polarization anisotropy of emission spectrum and intensity of light propagating in the diode organic layer have been observed. The mechanism of the emission anisotropy has been discussed in the periodic multilayer structure.
Growth of Epitaxial-Like (Sr0.5Ba0.5)Nb2O6 Ferroelectric Films
Authors: Lin Wen-Jen , Tseng Tseung-Yuen , Lin Sheuan-Perng , Tu Shun-Lih , Yang Sheng-Jenn , Harn Jenn-Jung , Liu Kuo-Shung , Lin I-Nan
Published: October 2002

Epitaxial-like (Sr0.5Ba0.5)Nb2O6 (SBN) films were successfully grown on (100) silicon substrates, using [002] CeO2 as the buffer layer and [00l] YBa2Cu3O7-
x

(YBCO) as the base electrode. The θ-2θ scan and φ-scan X-ray diffraction suggest that [210] SBN||
[100] YBCO||
[110]CeO2||
[110] Si. The ferroelectric hysteresis curves measured by the modified Sawyer-Tower technique show that the epitaxial-like SBN/YBCO/CeO2/Si films possess substantially better ferroelectricity than the polycrystalline SBN/Pt(Ti)/Si films. The remanent polarization (
P
r
) and coercive field (
E
c
) are, respectively, P
r=27.2 µ C/cm2 and E
c=24.8 kV/cm.
Observation of Conductance Quantization in A Novel Schottky In-Plane Gate Wire Transistor Fabricated by Low-Damage In Situ Electrochemical Process
Authors: Hashizume Tamotsu , Okada Hiroshi , Jinushi Keiichiro , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

A novel Schottky in-plane gate (IPG) quantum wire transistor has been successfully fabricated for the first time on a GaAs/AlGaAs quantum-well (QW) wafer, using a low-damage in situ electrochemical process. In comparison with previous IPG transistors of insulated-gate type, the present Schottky IPG device exhibited much better gate control of drain currents. In spite of large device dimensions of several hundred nanometers, sharp quantized conductance steps in units of 2e2/hwere observed up to 40 K as a result of the inherent strong electron confinement capability of the present IPG structure.
Relativistic Down-Shift Frequency Effect on the Application of Electron Cyclotron Emission Measurements to Medium Temperature Tokamak Plasmas*
Authors: Sato Masayasu , Isei Nobuaki , Shinichi Ishida Shinichi Ishida
Published: October 2002

The effects of relativistic down-shift frequency on the determination of the electron temperature profile from electron cyclotron emission (ECE) for medium temperature (2 keV≤Te≤10 keV) tokamak plasmas are studied. It has been found that the radial shift due to the relativistic effect is not negligible compared with the frequency resolution of present day ECE measurement systems. Therefore for precise measurement of the electron temperature profile it is necessary even in a medium temperature tokamak plasma to correct the shift due to relativistic down-shift frequency.
Transmission Electron Microscopic Observation of AlN/α-Al2O3 Heteroepitaxial Interface with Initial-Nitriding AlN Layer
Authors: Masu Kazuya , Nakamura Yukinori , Yamazaki Tsuyoshi , Shibata Tomohiko , Takahashi Michio , Kazuo Tsubouchi Kazuo Tsubouchi
Published: October 2002

The AlN/α-Al2O3 heteroepitaxial interface is investigated using a transmission electron microscope. The epitaxial AlN film is deposited by metalorganic chemical vapor deposition with and without initial nitriding. The initial nitriding method is to convert the α-Al2O3 substrate surface to a nanometer-thick AlN single-crystal buffer layer in NH3 ambient just before AlN deposition. The (1\bar210)AlN/(1\bar102)α-Al2O3 interface with initial nitriding is found to be atomically flat, and no dislocation inside the postdeposited AlN is observed. We have confirmed that initial nitriding is excellent in improving the crystal quality of the AlN epitaxial layer.
Magnetic Flux Distribution Induced by Pulsed Magnetic Field in Quench-and-Melt-Grown YBa 2Cu 3O 7-x
Authors: Toshihiko Itoh Toshihiko Itoh , Yoshinobu Tanimura Yoshinobu Tanimura , Takeo Takizawa Takeo Takizawa , Kohji Kanbara Kohji Kanbara
Published: October 2002

Flux movement generated by pulsed magnetic field has been observed using search coils coaxially set on the surface of a ring-shaped sample of quench-and-melt-grown YBa2Cu3O7-x
. From the analysis of these signals, we have found that the flux does not obey the critical state model, at least within the rising time of the pulsed field. This phenomenon is explained by the flux flow intensely driven by the Lorentz force under the external pulsed field.
Synchrotron Radiation Induced Decomposition of Closo-1,2-dicarbadodecaborane
Authors: Byun Dongjin , Hwang Seong-don , Zhang Jiandi , Zeng Hong , Perkins F. Keith , Vidali G. , Dowben P. A.
Published: October 2002

We have observed that molecular films ofcloso-1,2-dicarbadodecaborane ( C2B10H12) decompose due to exposure to synchrotron light. Dissociation results in films that form a heterogeneous intermediate phase between associative molecular fragments and solid, thin film boron-carbide. This heterogeneous phase has an observed electronic structure that is an admixture of the electronic structure observed for molecularly condensed orthocarborane and the electronic structure anticipated for rhombohedral boron-carbide (based on the B12icosahedral “building block”). With the synchrotron radiation exposure at room temperature there is dissociative adsorption of this icosahedral molecule and the growth of boron-carbide film is enhanced. The composition of the growing film changes for very thin films on Si(111), as determined by the boron to carbon ratio. The boron concentration of the film increases with increasing film thickness until the boron to carbon ratio reaches 5 when the film thickness is approximately 12 Å. After about 12 Å of film growth the composition is constant, i.e. B5C.
Behavior of Cu and Zn Impurities on GaAs Wafer Surfaces
Authors: Hiroshi Shibaya Hiroshi Shibaya
Published: October 2002

Surface Cu and Zn contamination levels of intentionally contaminated GaAs wafers were measured by total reflection X-ray fluorescence (TXRF). Cu and Zn are both major metallic impurities on GaAs wafer surfaces, but their adsorption behaviors in an organic base solution were quite different. Surface concentration of Cu was much higher than that of Zn when concentrations of Cu and Zn in the organic base solution were the same. Cleaning effects of running deionized water rinse in an ultrasonic bath (U-RDIW) were also studied. Surface concentrations of Cu and Zn were drastically reduced by U-RDIW rinse.
Fabrication of Highly Stable and Low Defect Density Amorphous Silicon Films at Low Substrate Temperature by Plasma Chemical Vapor Deposition Assisted with Piezoelectric Vibration
Authors: Sumiya Masatomo , Kawasaki Masashi , Koč Jan , Hideomi Koinuma Hideomi Koinuma
Published: October 2002

Plasma chemical vapor deposition (CVD) of a-Si:H films has been conducted under the application of piezoelectric vibration to the substrates with the expectation of enhancing the surface migration of the precursors. Defect density of the order 1015 cm-3 was achieved for a film deposited at 120° C under 2 MHz piezoelectric vibration. The photodegradation behavior of the deposited films was measured using irradiation by pulsed ruby laser as well as by Xe lamp. The prolonged light soaking increased the defect densities in the a-Si:H films as well as those in the films deposited by the conventional method, i.e., without the piezoelectric vibration. However, the saturated value for the former films remained at 3×1016 cm-3, significantly lower than the value ( ∼1017 cm-3) for the latter. The activation energy for recovery from the light-induced defect of a-Si:H was higher for the film deposited with piezoelectric vibration than the film deposited without the vibration. Thus, the piezoelectric vibration apparently functioned not only to reduce the defect density in as-deposited films but also to improve the stability against light soaking.
Highly Transparent and Conductive Zn2In2O5 Thin Films Prepared by RF Magnetron Sputtering
Authors: Minami Tadatsugu , Sonohara Hideo , Kakumu Toshikazu , Shinzo Takata Shinzo Takata
Published: October 2002

A new transparent conducting Zn2In2O5 film is demonstrated. The film was prepared by rf magnetron sputtering using binary compound targets composed of In2O3 and ZnO (with a Zn content (Zn/(Zn+In)) of 5-45 at%). The electrical properties were relatively independent of the substrate temperatures between room temperature and 350° C. A resistivity of 3.9×10-4 Ω· cm and an average transmittance above 80% in the visible range were obtained for undoped Zn2In2O5 films with a thickness of about 400 nm. The spatial resistivity distribution on the substrate surface was minimal for Zn2In2O5 films. Optical measurements showed a band-gap energy of about 2.9 eV and a refractive index of about 2.4 for Zn2In2O5. It was found that the resistance of the undoped Zn2In2O5 films was more stable than that of undoped ZnO or In2O3 films in oxidizing environments at high temperatures.
Anomalous Current-Voltage Characteristics and Threshold Voltage Shift in Implanted-Polysilicon-Gated Complementary Metal-Oxide-Semiconductor Field-Effect Transistors with/without Titanium-Polycide Technology
Authors: Chen Chii-Wen , Fang Yean-Kuen , Lee Gun-Yuan , Hsieh Jang-Cheng , Liang Mong-Song , Lin Mou-Shiung , Yoo Chue-San
Published: October 2002

The current-voltage (I-V) characteristics and threshold voltage (V
t) of implanted-polycrystalline surface channel complementary metal-oxide-semiconductor field-effect transistors (CMOSFETs) with and without titanium-polycided polycrystalline silicon gate structures are compared. We find that the earlier punch-through phenomenon is caused by boron (B) penetration into the gate oxide and channel regions in the boron-implanted p+-poly-silicon-gated device, and this degradation is reduced by using titanium-polycide (Ti-polycide) technology. However, this process results in a significant V
t shift. In addition, a detailed model for the kinetics of the B redistri-bution and the interface state generation during Ti-salicidation and after post thermal annealing is proposed to explain these phenomena.
Transport Properties of Bi-2212/Ag Superconducting Magnet with Ic over 500 A
Authors: Okada Michiya , Tanaka Kazuhide , Inoue Naomi , Sato Junichi , Kitaguchi Hitoshi , Kumakura Hiroaki , Kiyosi Tsukasa , Inoue Kiyoshi , Togano Kazumasa
Published: October 2002

A compact 3 T-class superconducting magnet has successfully been fabricated using 6 stacks of single pancake coils prepared from Bi-2212/Ag multifilamentary composite tapes. The dimensions of the magnet were 45 mm in height, 45 mm in outer diameter and 13 mm in clear bore. Maximum coil current reached 550 A (10-13 Ω· m), generating a magnetic field at the center B
0=3.1 T and maximum field of the magnet B
m=3.3 T without backup magnetic field. The J
c of the coil was estimated to be approximately 55% of the short-sample results. A single pancake coil generated B
m=0.42 T in a backup field of 20 T, although degradation of J
c due to large electromagnetic force was observed.
Use of Indium and Gallium as P-Type Dopants in Si 0.1 µm MOSFETs
Authors: Biesemans Serge , Stefan Kubicek Stefan Kubicek , Kristin De Meyer Kristin De Meyer
Published: October 2002

Devices with a channel length of 0.1 µm, employing In and B as p-type channel dopants, were fabricated to investigate the short channel effect. In this study, the benefits of using In instead of B are investigated with respect to the suppression of the short channel effect, the gate quality, the mobility and the long channel threshold voltage value. It is concluded that the use of In causes no direct complications. The advantage of using In lies in the suppression of the short channel effect. In this way, the conventional planar bulk device employing In as a channel implant can be scaled further at least for one generation of metal oxide semiconductor transistors without loss in current driveability. The feasibility of Ga as an ultra shallow p-type extension is also investigated.
Novel Low Leakage and Low Resistance Titanium Salicide Technology with Recoil Nitrogen Achieved by Silicidation after Ion Implantation through Contamination-Restrained Oxygen Free LPCVD-Nitride Layer (SICRON)
Authors: Kotaki Hiroshi , Nakano Masayuki , Hayashida Shigeki , Matsuoka Toshimasa , Kakimoto Seizou , Nakano Akihiko , Keichiro Uda Keichiro Uda , Yuichi Sato Yuichi Sato
Published: October 2002

A novel low leakage and low resistance titanium salicide process named “ silicidation after ion implantation through the contamination- restrained oxygen free LPCVD- nitride layer (SICRON)” has been developed. This novel oxygen free process has been successfully implemented in deep submicron dual gate CMOS (complementary metal oxide semiconductor) development. Junction leakage current for TiSi2-n+/p and -p+/n was reduced to the non-silicidation level. Furthermore, low sheet resistances of n+-and p+-gate electrode were maintained below the 0.2 µm line.
The Low-Temperature Characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs Broken-Gap Interband Tunneling Structures
Authors: Liu Meng Hwang , Wang Yeong Her , Houng Mau Phon , J. F. Chen J. F. Chen , Alfred Y. Cho Alfred Y. Cho
Published: October 2002

The characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling structures are investigated. In addition to the main negative differential resistance peaks, kinks or small peaks can be clearly seen, especially at low temperature. The effects of the heavy-hole states are expected to play an important role. Here, a k \cdotpp model incorporating the coupling effects of the heavy-hole states is used. It is found that the kinks and small peaks are the results of heavy-hole coupling. Furthermore, the electron distribution in the InAs emitter also contributes to the phenomena observed in the low-temperature characteristics.
Excellent Thermally Stable Epitaxial Channel for Implanted Planar-Type Heterojunction Field-Effect Transistors
Authors: Matsushita Shigeharu , Fujii Emi , Inoue Daijiro , Terada Satoshi , Banba Seiichi , Matsumura Kohji , Minoru Sawada Minoru Sawada , Yasoo Harada Yasoo Harada
Published: October 2002

We demonstrate for the first time that the decrease in the carrier concentration of highly doped GaAs layers caused by annealing is alleviated by thinning the layers. It is also suggested that the decrease is dependent on the Fermi energy in the doped layers. Thermally stable thin Si-doped GaAs channels are formed in implanted planar-type two-mode channel field-effect transistors (P-TMTs). A 0.2-µm device having a GaAs channel 9 nm thick with a doping level of 7×1018 cm-3 exhibits excellent performance, such as a transconductance g
m of 450 mS/mm, a current-gain cutoff frequency f
T of 72 GHz, and a maximum frequency of oscillation f
max of 140 GHz. Furthermore, it is indicated that highly doped thin layers are very effective for improving the DC and microwave performance of P-TMTs.
Impurity-free Disordering of InGaAs/InGaAlAs Quantum Wells on InP by Dielectric Thin Cap Films and Characterization of Its In-plane Spatial Resolution
Authors: J. Mondry Shinya Sudo , A. Coldren Larry
Published: October 2002

We have studied impurity-free disordering of InGaAs/InGaAlAs quantum wells on InP, induced by three different dielectric cap films, namely, SiO2, SiNx and SrF2. The difference in photoluminescence characteristics of these materials after heat treatment has been discussed. Furthermore, the in-plane spatial resolution of the disordering process has been investigated for the first time.
Damped Longitudinal Optical Phonon-Hole Plasmon Modes in p-Type GaAs
Authors: Ryoichi Fukasawa Ryoichi Fukasawa , Sidney Perkowitz Sidney Perkowitz
Published: October 2002

The effect of substantial plasmon damping on the frequencies and damping rates of the coupled longitudinal optical (LO) phonon-hole plasmon modes is examined by finding the complex roots of ε(ω)=0. The zeroes of the dielectric function ε(ω) give the frequencies of the longitudinal modes. The calculated results describe the anomalous downward shift and the single-mode behavior that we have observed previously for Raman spectra of the coupled modes in p-type GaAs.
Fabrication and Characterization of Novel Lateral Surface Superlattice Structure Utilizing Schottky Barrier Height Control by Doped Silicon Interface Control Layers
Authors: Seiya Kasai Seiya Kasai , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

A novel lateral surface superlattice (LSSL) structure based on the Schottky barrier height (SBH) difference produced by periodic insertion of Si interface control layer (Si ICL) stripes is proposed, fabricated and characterized. Two-dimensional computer simulation was first performed to gain information on basic design considerations. An electron-beam-induced current (EBIC) study on the fabricated device directly confirmed SBH modulation by Si ICL stripes. The devices showed periodic oscillations of drain conductance and transconductance at low temperatures up to 10 K. This behavior is distinctly different from that of previous split-gate devices. The mechanism of these oscillations was explained by a sequential resonant tunneling model. According to a quantitative analysis of the data, SBH difference of 70–150 meV was produced at the metal-semiconductor interface, which produced quantized levels with a separation of 2–3 meV at the heterointerface.
New Structure of 1.3 µm Strained-Layer Multi-Quantum Well Complex-Coupled Distributed Feedback Lasers
Authors: Kito Masahiro , Nakamura Shinji , Otsuka Nobuyuki , Masato Ishino Masato Ishino , Yasushi Matsui Yasushi Matsui
Published: October 2002

A new structure of 1.3 µm strained-layer multi-quantum well (MQW) complex-coupled distributed feedback lasers having an InAsP absorptive grating is demonstrated. In this structure, the InAsP absorptive grating and the strained-layer MQW active layer can be fabricated by a metalorganic vapor phase epitaxy process involving only one step. Furthermore, the fabricated laser has a low threshold current (16.8 mA) and a high efficiency (0.45 mW/mA).
High-Efficiency Monolithic Three-Terminal GaAs/Si Tandem Solar Cells Fabricated by Metalorganic Chemical Vapor Deposition
Authors: Soga Tetsuo , Yang Mingju , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

A monolithic GaAs/Si tandem solar cell which consists of a p+-n GaAs top cell and an n+-p-p+ Si bottom cell is fabricated by metalorganic chemical vapor deposition. The conversion efficiency of the top cell is increased by improvement of the solar cell structure (adoption of a graded band emitter layer) and optimization of the growth conditions (increase of the thermal annealing temperature and the growth temperature). By combining the conversion efficiencies of the GaAs top cell (16.0%) and Si bottom cell (3.9%), the active-area conversion efficiency of 19.9% (AM0, 1 sun) has been obtained in the three-terminal configuration.
Room-Temperature Operation of ZnSe-Active-Layer and ZnCdSe-Active-Layer Laser Diodes
Authors: Okuyama Hiroyuki , Nakayama Norikazu , Itoh Satoshi , Masao Ikeda Masao Ikeda , Akira Ishibashi Akira Ishibashi
Published: October 2002

Room-temperature operation of a ZnSe-active-layer double-heterostructure laser diode (LD) was observed. The lasing wavelength was 471 nm. The emission energy shift with increasing current is explained by band filling and band-gap shrinkage. The threshold carrier density is calculated to be 4×1018 cm-3. We conclude that the dominant lasing mechanism of II–VI double heterostructure laser diodes is the recombination of electron-hole plasma. It is also the dominant mechanism in ZnCdSe quantum-well separate-confinement-heterostructure laser diodes. In both types of LD's, the band-gap shrinkage was observed near the threshold.
Impact of Negative-Bias Temperature Instability on the Lifetime of Single-Gate CMOS Structures with Ultrathin (4–6 nm) Gate Oxides
Authors: Ogawa Shigeo , Masakazu Shimaya Masakazu Shimaya , Noboru Shiono Noboru Shiono
Published: October 2002

The lifetime of ultrathin gate oxides under low-field stress conditions has been studied on the basis of empirical acceleration equations for negative-bias temperature instability (NBTI) up to 5000 hours for 4.2-to-30-nm-thick oxides of metal-oxide-silicon (MOS) structures. The derived lifetime, the maximum acceptable oxide field, and the maximum acceptable operating voltage are found to be strongly dependent on the reliability specification. Since the number of interface traps induced by NBTI is inversely proportional to the oxide thickness, this instability becomes an important factor limiting the lifetime of single-gate CMOS structures with ultrathin gate oxides.
Densified SiOF Film Formation for Preventing Water Absorption
Authors: Kudo Hiroshi , Shinohara Rika , Takeishi Shunsaku , Awaji Naoki , Masao Yamada Masao Yamada
Published: October 2002

We confirmed that the density of a SiOF film was decreased by the addition of C2F6 as a fluorine source. Such a decrease in the density had the most significant effect on the water absorptivity. Densities of the films were controlled by increasing O2 gas mixture ratios. From the TDS measurements of water desorption and the change in dielectric constants which occurred when the film was exposed to atmosphere, we confirmed that the densified films had lower water absorptivity.
Undercooled Liquid Viscosity and Glass Formation of a Mg62Cu26Y12 Alloy
Authors: Wu Shyue-Sheng , Chin Tsung-Shune , Su Kuo-Chang , Shyr Fuh-Shuenn
Published: October 2002

The glass forming ability of a Mg62Cu26Y12 alloy was delineated by theories of crystallization kinetics. The viscosity of the molten Mg62Cu26Y12 alloy above its melting point was measured by using a rotational viscometer. The temperature dependence of the viscosity derived from the free volume theory was extrapolated to the undercooled liquid region by the Fulcher-Vogel expression, i.e., η=5.78×10-5exp
[7293.6/(T-255.6)] where η is given in cP and T in K. Furthermore, the C–C–T curve was derived from the isothermal crystallization T–T–T curve which had been constructed based on the mechanism of homogeneous nucleation and crystal growth. From such a curve, the critical cooling rate required to form glassy state was derived to be 98° C/s.