bluuebunny/crossref_metadata_2025 huggingface dataset:
NdBa2Cu3OX–Au–NdBa2Cu3OX Proximity-Effect Junction with a Decanano-Scale Trench Fabricated Using a High-resolution Focused Ion Beam Technique
Authors: Shin'ichi Morohashi Shin'ichi Morohashi , Youichi Enomoto Youichi Enomoto
Published: October 2002

We have fabricated NdBa2Cu3O

X

–Au–NdBa2Cu3O

X

proximity-effect junctions using a high-resolution focused gallium-ion beam (FIB) technique with a full width of half maximum of 10 nm. These bridge-type junctions have characteristics such as a decanano-scale trench for the bridge formed using the etching function of FIB, and a precise contact area defined using the deposition function of FIB. The current-voltage characteristics of the junctions are qualitatively consistent with a resistively shunted junction model.
Phenomenological Approach to the Dependence of Magnetic Anisotropy on Co Layer Thickness in Epitaxial Au/Co and Au/Co/Ag Superlattices
Authors: Toshiki Kingetsu Toshiki Kingetsu
Published: October 2002

Co-layer-thickness (t) dependences of magnetic anisotropy energies (K
eff) in epitaxial (111)Au/Co and (111)Au/Co/Ag superlattices are interpreted phenomenologically. Saturation of K
eff
t at small t in a t-K
eff
t plot is attributed to two nonidentical interfaces of each Co layer and the gradient of Co-layer in-plane strain in the thickness direction. The strains are estimated from the results of in situ reflection high-energy electron diffractometry, which were reported earlier, taking electron penetration to the near-surface regions into account. The magnetoelastic interface anisotropy contributing to the perpendicular magnetic anisotropy is suggested to arise from a larger magnetoelastic constant than that in bulk Co, which is in agreement with recent theoretical calculations.
Control of Nematic Liquid Crystal Alignment Using Stripped Film Method
Authors: Yasushi Kawata Yasushi Kawata , Yasushi Mori Yasushi Mori
Published: October 2002

We have previously reported that the surface of a substrate fabricated using the stripped film method gives a uniform orientation of both the nematic director and pretilt angle. However, this alignment layer generates only a low pretilt angle of about 1.5°. The stripped film surface fabricated using the substrate constructed with three kinds of organic film, polyvinyl alcohol base film (Vinylon film, KURARAY Co.), polyvinyl alcohol (PVA) adhesive agent and polyimide film (AL-3046, Japan Synthetic Rubber Co.), generated unique characteristics of the pretilt angle of nematic liquid crystals. We propose under certain process conditions, the stripped film surface is capable of generating a high pretilt angle of about 10° which is much higher than the pretilt angles of the polyimide and PVA alignment layers fabricated by the conventional rubbing method.
Interfacial Stability Between Ta–Sn–O Films and Indium Tin Oxide Electrodes
Authors: Satoh Toshikazu , Fujikawa Hisayoshi , Ishii Masahiko , Takeshi Ohwaki Takeshi Ohwaki , Yasunori Taga Yasunori Taga
Published: October 2002

Interfacial structures between Ta2O5–SnO2 (Ta–Sn–O) films and indium tin oxide (ITO) electrodes were studied using transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS). It was found that indium atoms diffused into the Ta2O5 film by annealing (at 923 K for 30 min in N2 atmosphere), while diffusion was not observed at the Ta–Sn–O/ITO interface. The thermal stability of the interfaces of Ta2O5/ITO and Ta–Sn–O/ITO can be explained in terms of the difference of the diffusion behavior at the interface, which affect the superior electrical properties of the Ta–Sn–O/ITO structures.
Investigation of Degradation in Homoepitaxially Grown ZnCdSe/ZnSe Light Emitting Diode
Authors: Ohno Tetsuichiro , Akira Ohki Akira Ohki , Takashi Matsuoka Takashi Matsuoka
Published: October 2002

From the transmission electron microscope (TEM) observation of ZnSe homoepitaxial films, it is clarified that the major pre-existing defects in the film are Shockley extended dislocations. Correlation between the etch pits and the Shockley extended dislocations are also confirmed. The degradation mode of a ZnCdSe/ZnSe homoepitaxial light emitting diode (LED) is discussed on the basis of the microscopic observation. Many dark spot defects (DSDs) are observed in the emission pattern just after turn-on, and they enlarge and become pronounced keeping their round shape. The growth velocity of the DSD is less than 0.056 µm/min for the current density of 408 A/cm2. The DSD density is almost the same as the etch pit density (EPD) of the as-grown LED wafer.
Emission of O- Radical Anions from a Solid Electrolyte Surface into the Gas Phase
Authors: Torimoto Yoshifumi , Harano Azuchi , Suda Toshiyuki , Sadakata Masayoshi
Published: October 2002

We have observed the emission of O- radical anions from a solid electrolyte surface. A simple experimental apparatus was designed to incorporate a gap between a YSZ (yttria stabilized zirconia) anode and a stainless steel space electrode. By applying a DC voltage of 100 V across the gap, O- radical anions and electrons were produced which could be detected using a quadrupole mass spectrometer. Recently, Greber et al.. reported the observation of O- radical anion emission from a cesium-coated surface when the surface was exposed to thermal oxygen molecules. However, this method cannot maintain O- emission without adsorbed oxygen molecules. In the present work, the possibility of obtaining continuous emission of O- from a YSZ surface was examined.
Homodyne Laser Interferometer
Authors: Zu Wen Chao Zu Wen Chao
Published: October 2002

A homodyne laser interferometer which, upon projecting two beams from a two-frequency laser source onto a moving target, interprets, by employing a frequency-count-addition process, two Doppler frequency shifts, each occurring from each beam when the beams are returning to the interferometer. The conceptual system structure and the principle of signal processing are described.
Laser Micromachining of Silicate Glasses Containing Silver Ions Using a Pulsed Laser
Authors: Tadashi Koyama Tadashi Koyama , Keiji Tsunetomo Keiji Tsunetomo
Published: October 2002

Suitable glasses for laser micromachining using a Nd:YAG laser have been developed. These glasses contain Ag ions introduced using the ion exchange technique. After machining with the 2nd and 3rd harmonic beams of a pulsed Nd:YAG laser, the irradiation region has a smooth surface without microcracking. A phase mask pattern is successfully transcribed on the glass surface through machining with a 355 nm pulsed beam. The irradiation area acts as a surface-relief grating.
Behavior of Defects in Heavily Boron Doped Czochralski Silicon
Authors: Ono Toshiaki , Asayama Eiichi , Horie Hiroshi , Hourai Masataka , Sano Masakazu , Nakai Hideki Tsuya
Published: October 2002

Defect behaviors in heavily boron doped silicon, with boron concentration ranging from 7.1×1017 to 3.1×1019 atoms/cm3, were studied using transmission electron microscopy. The oxygen precipitation and the change of the precipitate morphology from plate to polyhedral were observed to be enhanced with increasing boron concentration. However, in wafers with the highest boron concentration, precipitate density decreased, and aggregations of small polyhedral precipitates on the {110} planes were observed. It was also found that as the boron concentration was increased, the precipitate size reduced and the type of secondary induced defects changed from punching-out dislocations to stacking faults due to the reduction in a crystal lattice strain.
Effect of the Surface-Atomic Positions on Reflectance Difference Spectra of [001]-GaAs β2 Structure
Authors: Misao Murayama Misao Murayama , Takashi Nakayama Takashi Nakayama
Published: October 2002

The role of surface atomic positions in reflectance difference (RD) spectra of the GaAs(001)-(2 ×4)β2 structure is studied using the s
p
3
s
* tight-binding method. Here we assume that the surface atomic positions are effectively changed by variation of two kinds of transfer energies. It was found that the As-As distance change in surface As dimer causes an energy shift of the RD spectral peak, while the distance change between surface As and substrate Ga affects not the peak position but the peak width. These calculation results are compared with the results of recent experiments.
Computer Simulation of Sputtering of Tungsten due to Simultaneous Bombardment with Deuterium, Carbon and Oxygen Ions in Plasmas
Authors: Kaoru Ohya Kaoru Ohya , Jun Kawata Jun Kawata
Published: October 2002

A computer simulation code which treats the erosion and deposition processes for divertor plates in magnetic confinement fusion devices is developed. The simulation code allows simultaneous incidence of three ion species, as well as a Maxwellian distribution and different charge states of the projectiles. The dynamic composition change of the surface layer due to projectile implantation and collisional transport of solid atoms (no diffusion and segregation), and redeposition of sputtered atoms due to their ionization and gyromotion in a scrape-off layer (SOL) plasma, are taken into account. This code is applied to sputtering of tungsten bombarded simultaneously by D+ (88%), C3+ (6%) and O3+ (6%) ions at the SOL temperature of 40 eV.
Si Oxynitridation with Helicon-Wave Excited Nitrogen Plasma: Effects of Plasma Divergence and Concentration on Substrates
Authors: Shinjiro Kimura Shinjiro Kimura , Tetsuya Ito Tetsuya Ito , Masato Tabakomori Masato Tabakomori , Yoshinaga Okamoto Yoshinaga Okamoto , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Si was oxynitrided with helicon-wave excited \Nii and Ar mixed plasma. The flow-rate ratio (\Nii :Ar) was kept constant (8:2). Oxynitridations were performed in two growth geometries in which plasma was either concentrated on the substrate or diverged from the substrate using permanent magnets. In the case of plasma concentration, relatively uniform Si oxynitride (probably \Sii \Nii O) was formed throughout the entire depth of the film. In the case of plasma divergence, however, only Si oxide was grown. Therefore, the presence of nitrogen ions is concluded to be essential for oxynitridation of Si.
Tight-Binding Calculation of Electronic Structures of InNAs Ordered Alloys
Authors: Yang Tao , Sadanojo Nakajima Sadanojo Nakajima , Shiro Sakai Shiro Sakai
Published: October 2002

The electronic structure of InN

x

As1-
x

ordered alloys (x=0.25, 0.5 and 0.75) are calculated based on a semi-empirical tight-binding method. The alloy is found to have direct band gaps throughout the entire composition range. The band-gap bowing parameter c in E
g=0.36+1.53x+c
x(x-1) eV of the alloy InN

x

As1-
x

is larger with larger valence-band discontinuity between InAs and InN, and is 4.22 eV if a theoretical value of 3.79 eV given by Harrison's theory is assumed.
X-Ray and Photoluminescence Characterization of a Strain-Free GaAs-on-Si Structure Formed by Annealing under Ultrahigh Pressure
Authors: Takehito Jimbo Takehito Jimbo , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Characteristics of strain-free GaAs-on-Si structures formed by annealing under ultrahigh pressure were investigated by X-ray diffraction (XRD) analysis and photoluminescence (PL) measurement. It was found that a strain-free GaAs film was formed on a Si substrate without serious degradation of the optical and crystallographical properties of the film. It was also found that no additional strain or defects were generated during PL measurement at 77 K. Next, the strain-free GaAs-on-Si structure was reannealed at atmospheric pressure, and variation of the strain was investigated. It was found in this experiment that the strain in the GaAs film increased rapidly in the first 5 min of reannealing but within 20 to 30 min it reached to a constant value which was determined by the reannealing temperature. Finally, both XRD and PL data were compared and an intensity result on the depth distribution of strain in a GaAs film was derived.
Improvement in Aging Characteristics by Zn Doping of Electron-Beam Evaporated SrS:Ce Thin-Film Electroluminescent Devices
Authors: Ohmi Koutoku , Hirose Tomoji , Harada Mitsunori , Shosaku Tanaka Shosaku Tanaka , Hiroshi Kobayashi Hiroshi Kobayashi
Published: October 2002

Aging characteristics of electron-beam evaporated SrS:Ce thin film electroluminescent devices have been improved by using a SrS:Ce and ZnS mixture source pellet. For the Zn-doped device, luminance is maintained at more than 60% of the initial value and threshold voltage remains constant for more than 1000 hours of aging at 500 Hz drive. A rapid decrease in luminance corresponds to a decrease in dynamic space charge, and is reduced by Zn doping. In contrast, a slow decrease in luminance is attributed to a change in the electron emission characteristics of phosphor-insulator interfaces.
Efficiency of Boron Gettering for Iron Impurities in p/p+ Epitaxial Silicon Wafers
Authors: Miyazaki Morimasa , Miyazaki Sumio , Ogushi Satoshi , Ochiai Takashi , Masakazu Sano Masakazu Sano , Tatsuhiko Shigematsu Tatsuhiko Shigematsu
Published: October 2002

The evaluation of B gettering for Fe impurities in p/p+ Si epitaxial wafers was carried out, after intentional Fe contamination, by measuring the Fe concentration in the epitaxial layer using deep level transient spectroscopy (DLTS). As the surface [Fe] before diffusion was increased, [Fe] in epitaxial layer also increased. As B concentration in the p+ substrate was raised, B gettering efficiency became higher. On comparison of the experimental results with the segregation gettering model, it was concluded that B gettering for Fe does not occur at a high temperature such as 800° C or 1100° C. B gettering for Fe can be inferred to occur below 600° C during the cooling process.
Correlation between Surface Microroughness of Silicon Oxide Film and SiO2/Si Interface Structure
Authors: Masatoshi Ohashi Masatoshi Ohashi , Takeo Hattori Takeo Hattori
Published: October 2002

It was found, from combined measurements of the surface microroughness of silicon oxide film and the SiO2/Si interface structure, that the surface microroughness of thermal oxide film formed on a Si(111) surface changes periodically with the progress of oxidation in accordance with periodic changes in interface structures. Therefore, the changes in interface structures can be detected by measuring the oxidation-induced surface microroughness.
Vibrational Stimulated Raman Emission from Dibromomethane as Seed Beam for Four-Wave Rotational Raman Mixing in Hydrogen
Authors: Lin Cheng-Huang , Takayuki Ohnishi Takayuki Ohnishi , Totaro Imasaka Totaro Imasaka
Published: October 2002

A portion of Nd:YAG laser emission is used as a pump beam for neat dibromomethane to generate vibrational stimulated Raman emission emitting at a Raman shift frequency of 588 cm-1. This beam is aligned to be collinear with the other portion of the pump beam and is used as a seed beam for the generation of numerous rotational stimulated Raman emissions of hydrogen with a Raman shift frequency of 587 cm-1. Because their Raman shift frequencies coincide, a multifrequency laser emission consisting of many rotational lines, in addition to vibrational lines, is generated by four-wave rotational Raman mixing.
Growth of Cubic Boron Nitride Thin Films on GaAs by Reactive Vapor Phase Transport
Authors: Jaime Mimila-Arroyo Jaime Mimila-Arroyo
Published: October 2002

Thin films of cubic boron nitride have been grown on (100) GaAs by Reactive Vapor Phase Transport using water vapor as transporting gas. X-ray diffraction shows that only the cubic phase is present in these layers, and that they have a lattice parameter of 3.597 Å, as well as that the [111] direction seems to be a preferential one for the growth of this material on (100) GaAs. Scanning electronic microscopy reveals smooth surfaces, absence of voids in the layers and clean interfaces between the layers and the substrate. The films have shown excellent stability as after several months of being exposed unprotected to the air their properties did not change at all.
Low Temperature Direct Silicon Wafer Bonding Using Argon Activation
Authors: Robert W. Bower Robert W. Bower , Frank Y.-J. Chin Frank Y.-J. Chin
Published: October 2002

We have observed that silicon surfaces activated in an Ar plasma form very strong bonds after a low temperature anneal. However, voids formed by Ar gas bubbles develop during the annealing process. This work provides insight into generalized plasma assisted bonding of material surfaces used in micro-(electronic/optical/mechanical) devices.
Growth of GaN and Al0.2Ga0.8N on Patterened Substrates via Organometallic Vapor Phase Epitaxy
Authors: Nam Ok-Hyun , Bremser Michael D. , Ward Brandon L. , Nemanich Robert J. , Robert F. Davis Robert F. Davis
Published: October 2002

The selective growth of GaN and Al0.2Ga0.8N has been achieved on stripe and circular patterned GaN/AlN/6H-SiC(0001) multilayer substrates. Growth morphologies on the stripe patterns were a function of the widths of the stripes and the flow rate of triethylgallium. No ridge growth was observed along the top edges of the truncated stripe patterns. Smooth (0001) top facets formed on stripes ≥5 µ m wide. Uniform hexagonal pyramid arrays of undoped GaN and Si-doped GaN were successfully grown on 5 µ m circular patterns. Field emission measurements of a Si-doped GaN hexagonal pyramid array exhibited a turn-on field of 25 V/µ m for an emission current of 10.8 nA at an anode-to-sample distance of 27 µ m.
Nonlinear Optical Response from Excitons in Soliton Lattice Systems of Doped Conducting Polymers
Authors: Kikuo Harigaya Kikuo Harigaya
Published: October 2002

Exciton effects on conjugated polymers and the resulting optical nonlinearities are investigated in soliton lattice states. We use the Su-Schrieffer-Heeger model with long-range Coulomb interactions for electrons. The third-harmonic generation (THG) at off-resonant frequencies is calculated as functions of the soliton concentration and the chain length of the polymer. The magnitude of the THG with 10 percent doping increases by the factor of about 102 from that of the neutral system. The large increase of the order two is common for several Coulomb interaction strengths, and is seen in open systems as well as in periodic systems.
All-Solid-State, THz Radiation Source Using a Saturable Bragg Reflector in a Femtosecond Mode-Locked Laser
Authors: Sarukura Nobuhiko , Liu Zhenlin , Ohtake Hideyuki , Izumida Shinji , Yamanaka Takaya , Segawa Yusaburo , Itatani Taro , Sugaya Takeyoshi , Nakagawa Tadashi , Sugiyama Yoshinobu
Published: October 2002

We have demonstrated a new scheme for generating intense far-infrared or THz radiation pulses synchronously with near-infrared pulses using a saturable Bragg reflector placed inside a mode-locked laser cavity. With this newly proposed simple scheme, THz radiation which peaked at around 0.66 THz, with an average power of 2–3 nW is directly generated synchronously with femtosecond near-infrared optical pulses.
Defects in Langmuir-Blodgett Film of Cadmium Arachidate Detected with Atomic Force Microscopy
Authors: Nechev George , Masahiro Hibino Masahiro Hibino , Ichiro Hatta Ichiro Hatta
Published: October 2002

Molecular-resolution images of the surface of cadmium arachidate Langmuir-Blodgett (LB) films were obtained using an atomic force microscope under ambient conditions. The well-preserved raw image confirmed the periodic buckling superstructure and revealed an edge dislocation in the LB films.
Injection of Mass-Selected Ions into a Quadrupole Ion Trap
Authors: Hall Stuart G. , Murakami Hirohiko , Palmer Richard E. , Kanayama Toshihiko
Published: October 2002

A simple ion trap has been developed, which captures and confines ions using the fringing field of a linear ac quadrupole. The trap consists of a quadrupole electrode that has one end surrounded by a cage electrode. Ions generated outside the trap are injected through the internal field of the quadrupole and subsequently trapped in the external field extending to the cage. Theoretical calculations and experiments show that when Ar+ ions are injected into the trap at an ac frequency, f, of 1.2 MHz, the chirping of f to 0.6 MHz over ∼50 µ s improves the trap lifetime. This effect arises due to the adiabatic change in the trapping potential, which closes the injection pathway of the ions into the trap.
Carrier Density of Epitaxial InN Grown by Plasma-Assisted Metalorganic Chemical Vapor Deposition
Authors: Michio Sato Michio Sato
Published: October 2002

InN epitaxial layers were grown on (0001) sapphire substrates by plasma-assisted metalorganic chemical vapor deposition, by which large amounts of radicals can be supplied to a surface with little ion damage, using triethylindium and nitrogen radicals as the precursors. Low carrier densities were achieved at a growth temperature of 600° C, which was the highest temperature to grow InN without forming In droplets. Probably because of the slow reaction rate of In–N bond formation, lowering the growth rate was more important than increasing the nitrogen-radical flux. A carrier density of only 4×1019 cm-3 was achieved.
Improvement of SiO 2 Properties by Heating Treatment in High Pressure H 2O Vapor
Authors: Toshiyuki Sameshima Toshiyuki Sameshima , Mitsuru Satoh Mitsuru Satoh
Published: October 2002

Properties of SiO2 and SiO2/Si interfaces formed by plasma chemical vapor deposition were improved by heating at 270°C in high pressure H2O vapor. The treatment reduced the fixed oxide charge density from 2.5×1012 cm-2 (initial) to 8×1010 cm-2 as the H2O vapor pressure increased to 54 bar. The peak frequency of the absorption band caused by the Si-O antisymmetric stretching vibration mode was increased to 1078 cm-1 for treatment with 54 bar H2O vapor, while it was 1062 cm-1 before the treatment. The full width at half-maximum of the absorption band was reduced to 65 cm-1.
Electrooptical Effects of “Single-Crystalline” Films of Ferroelectric Copolymers of Vinylidene Fluoride and Trifluoroethylene
Authors: Tajitsu Yoshiro , Fujii Masaki , Suzuki Hirochika , Aoki Masaru , Koji Suzuki Koji Suzuki , Hiroji Ohigashi Hiroji Ohigashi
Published: October 2002

“Single crystalline” (SC) films of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymers (P(VDF/TrFE)) which are highly double-oriented films, do not form an intricate highly ordered structure, for example, a lamellar structure, but a simple one. After a SC film is poled under a dc electric field, one-to-one correspondence can be observed between the macro-(drawn and poling axes) and optical axes in a SC film of P(VDF/TrFE). Therefore, linear electrooptical effects of SC films of P(VDF/TrFE) can be measured at room temperature and constant stress. We then found a large electrooptical coefficient in SC films of P(VDF/TrFE).
Near Room-Temperature Growth of SiO2 Films for p-HgCdTe Passivation by Liquid Phase Deposition
Authors: Houng Mau-Phon , Wang Yeong-Her , Wang Na-Fu , Chien-Jung Huang Chien-Jung Huang , Wai-Jyh Chang Wai-Jyh Chang
Published: October 2002

We first propose a low temperature process (35° C–45° C) for the growth of high-quality SiO2 layer on p-HgCdTe by liquid phase deposition (LPD). In this new formation technology, the surface of HgCdTe substrates was treated with suitable ammonia solution to enhance the generation of OH- radicals which is favorable to the formation of SiO2 films. The refractive index of the SiO2 films is close to 1.465 under the typical growth conditions. The leakage current, surface charges density, and dielectric breakdown strength of the test samples, measured at 77 K, are found to be 0.356 nA (at -5 V), -7.04×1010/ cm2, and 650 kV/cm, respectively which are comparable to other techniques. The film quality demonstrates its potential in fabricating infrared devices.
Effects of Adsorption Kinetics on the Low-Temperature Growth-Rate Activation Energy in Si Gas-Source Molecular Beam Epitaxy
Authors: Nakazawa Hideki , Miyamoto Maki Suemitsu
Published: October 2002

Low-temperature growth-rate activation energy E
g for the growth of Si hydrides and the hydrogen desorption energy E
d from Si surfaces are shown to differ from each other (E
g<E
d) as opposed to E
g=E
d, which has been frequently postulated. A comparative growth study of silane and disilane gas-source molecular beam epitaxy clarifies that this difference arises from non-negligible contributions from the adsorption kinetics in the formation of E
g. Based on this knowledge, a method for determining the true E
d values is presented, and its validity is demonstrated by a successful reduction to an identical E
d value (2.0 eV), which was determined from much less, and mutually different E
g values of silane and disilane growth.
Field-Effect Mobility of Molecularly Doped Poly(3-hexylthiophene)
Authors: Kazuya Tada Kazuya Tada , Hiroshi Harada Hiroshi Harada , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Thin film field-effect transistors (TFTs) utilizing poly(3-hexylthiophene) (PAT6) doped with the electron transporting molecule N,N'-bis(2,5-di- tert -butylphenyl)-3,4,9,10-perylene dicarboximide (BPPC), have been fabricated and characterized. Bipolar transport characteristics have been found in these TFTs, for which the mobilities of both the hole and the electron have been evaluated. Observed unique BPPC concentration dependence of the field-effect electron mobilities has been interpreted in terms of the percolation model.
Resolution-Limit Study of Chain-Structure Negative Resist by Electron Beam Lithography
Authors: Manako Shoko , Fujita Jun-ichi , Ochiai Yukinori , Eiichi Nomura Eiichi Nomura , Shinji Matsui Shinji Matsui
Published: October 2002

We found that low-molecular-weight polystyrene with a chain structure acts as a 10-nm-level high-resolution negative resist in electron beam lithography. The resolution limit is proportion to the molecular weight of the polystyrene resist. The size of the polystyrene resist dot patterns which can be formed decreased with decreasing molecular weight of the polystyrene. Dot patterns of nearly 10 nm in diameter can be formed by a polystyrene resist with a molecular weight of 800.
GaN Thin Film Growth on LiGaO 2 Substrate with a Multi-Domain Structure
Authors: Yasuo Tazoh Yasuo Tazoh , Takao Ishii Takao Ishii , Shintaro Miyazawa Shintaro Miyazawa
Published: October 2002

We investigated the differences in the growth morphologies of hexagonal GaN thin films on {001}LiGaO2 substrates with a multi-domain structure. GaN thin films grown on one domain, where the etching rate was high using an aqueous solution of nitric acid (H2O:HNO3=1:1), peeled off. On the other hand, GaN thin films with good crystallinity grew epitaxially on the other domain, where the etching rate was low. These results strongly suggest that the peeling-off of GaN film from a {001}LiGaO2 substrate must be closely related to the differences in the chemical stability and/or polarity of the two domains.
Thermodynamic Analysis on Molecular Beam Epitaxy of GaN, InN and AlN
Authors: Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

A chemical equilibrium model is applied to the Molecular Beam Epitaxy (MBE) growth of GaN, InN and AlN semiconductors using atomic nitrogen and NH3 sources. The equilibrium partial pressure and the growth rate are calculated for each of the following parameters: input V/III ratio, input partial pressure of group III elements and growth temperature. A phase diagram for the deposition, indicating etching, droplet and growth regions, is computed for the growth of III–V nitrides. Based on the diagram, the growth condition suitable for the MBE growth of III–V nitrides is predicted.
Growth of A-Axis-Oriented YBa 2Cu 3Ox
Films on Gd 2CuO 4 Buffer Layers
Authors: Masashi Mukaida Masashi Mukaida
Published: October 2002

A-axis-oriented YBa2Cu3O
x
films are grown on lattice matched Gd2CuO4 buffer layers with a K2NiF4-type structure on (100) SrLaGaO4 substrates by pulsed laser deposition from the viewpoint of atomic graphoepitaxy. The preferred orientation and in-plane orientation are investigated in the films grown at various substrate temperatures. In-plane aligned a-axis-oriented YBa2Cu3O
x
films are grown in a relatively wide temperature range by using a new Gd2CuO4 buffer layer. The b
c-plane lattice matched K2NiF4 (100) substrate surfaces widen the growth conditions of in-plane aligned a-axis-oriented YBa2Cu3O
x
films.
Field Emission from an Ion Irradiated Photoresist
Authors: Tanemasa Asano Tanemasa Asano , Eiji Shibata Eiji Shibata , Daisuke Sasaguri Daisuke Sasaguri , Kenji Makihira Kenji Makihira , Katsuya Higa Katsuya Higa
Published: October 2002

The field emission from Ar ion irradiated photoresist material is demonstrated. A photoresist of novolac-type positive-tone is used as the test material. The electrical resistivity of the photoresist film is found to decrease after Ar ion implantation at doses on the order of 1016 cm-2. Raman spectroscopy shows that carbon-carbon bonds such as the graphite bond are produced due to ion bombardment. For the field emission, a pyramid-like structure is prepared using oxygen-plasma etching and Ar ions are implanted to the pyramid-like structured photoresist. Electron emission of the order of 10-6 A is observed for implanted samples, while no emission is detected from unimplanted samples.
Loss Processes of CF and CF 2 Radicals in the Afterglow of High-Density CF 4 Plasmas
Authors: Suzuki Chihiro , Koichi Sasaki Koichi Sasaki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

The decay time constants of CF and CF2 radical densities were measured in the afterglow of high-density CF4 plasmas by laser-induced fluorescence spectroscopy. As a result, it was found that the lifetime of CF radicals was shorter than the geometrical diffusion time determined by the chamber design. This indicates the presence of fast loss processes of CF radicals in the gas phase. The lifetime of CF2 radicals was always longer than the geometrical diffusion time, and was almost linearly dependent on the gas pressure. The diffusion coefficient and the surface loss probability of CF2 were evaluated simultaneously from the pressure dependence of the decay time constant.
Submicrometer-Sized Organic Light Emitting Diodes with a Triphenylamine-Containing Polycarbonate as a Guest Molecule in a Polymer Blend
Authors: Hibino Chihaya Adachi , Toshiki Koyama Toshiki Koyama , Yoshio Taniguchi Yoshio Taniguchi
Published: October 2002

We fabricated submicrometer-sized organic light emitting diodes (OLED) with bright emission using a polymer blend. The cell structure was composed of ITO (indium-tin oxide)/hole transport layer (polymer blend layer)/emitter layer/MgAg. We used poly (methyl methacrylate) (PMMA) as an inert host material and N,N′-diphenyl- N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine-polycarbonate (PC-TPD) as a guest material. The PC-TPD formed submicrometer-sized spherical domains, actually prolate spheroids, in the PMMA host layer. With 2 wt% of PC-TPD, the domain diameters were around 200 nm according to atomic force microscopy (AFM) observation. The OLED including such a blend structure appeared as an array of bright submicrometer-sized electroluminescence spots. The number of working diodes exceeded four million per square centimeter.
Photosurface Deposition of Ag on Ag-Rich Ag–Ge–S Films: Analysis of Change in the Optical Transmission Spectra
Authors: Takeshi Kawaguchi Takeshi Kawaguchi , Shigeo Maruno Shigeo Maruno
Published: October 2002

Change in optical transmission spectra due to the photosurface deposition phenomenon has been explained in terms of the growth of photodeposited Ag particles and a decrease in the Ag concentration of the illuminated Ag-rich Ag–Ge–S film. The marked decrease in transmission at wavelengths in the range of 700–800 nm was found to be due to an increase in the surface area occupied by the Ag particles. Photodeposition of fine Ag particles is an important factor for the application of Ag-rich chalcogenide films to high-density erasable optical recording devices.
Novel Terahertz Radiation from Flux-Trapped YBa 2Cu 3O 7-
δ Thin Films Excited by Femtosecond Laser Pulses
Authors: Masayoshi Tonouchi Masayoshi Tonouchi , Masahiko Tani Masahiko Tani , Zhen Wang Zhen Wang , Kiyomi Sakai Kiyomi Sakai , Noboru Wada Noboru Wada , Masanori Hangyo Masanori Hangyo
Published: October 2002

We discovered a new type of terahertz (THz) radiation from YBa2Cu3O7-δ thin films. Ultrashort electromagnetic pulses, which are referred to as THz radiation, were emitted into free space by irradiating the superconductive films with femtosecond laser pulses. The THz radiation, with a spectrum extending from 0.1 to 3 THz, was excited in both the films applied with a magnetic field and the flux-trapped films. The results suggest that the screening current for the external magnetic field and circulating current around the trapped flux play an important role in the emission mechanism.
Observation of the Structure and its Formation Process of a New Volumetric Coulomb Cloud Composed of Different Multiple Dust Layers
Authors: Nunomura Shota , Noriyasu Ohno Noriyasu Ohno , Shuichi Takamura Shuichi Takamura
Published: October 2002

A three-dimensional funnel-shaped dust cloud composed of multiple layers with different sized dust particles has been clearly observed in a new configuration of DC glow discharge. The Coulomb crystal-like cloud seems to be supported against gravity by the electric field in the thick sheath above the mesh cathode, in which the heavier layer of dust cloud seems to push the sheath to have a greater electrostatic force. The structural formation process of such a new volumetric Coulomb cloud was observed by a video imaging technique with laser light scattered by moving dust particles. They seem to be transported from the far outside, attach to the lateral surface of the funnel, and build up. The cloud is observed to expand radially outward on the horizontal layer.
A Study on the Relation between Film Quality and Deposition Rate for Amorphous Silicon Films Grown by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition Using H 2/SiH 4
Authors: Moonsang Kang Moonsang Kang , Jaeyeong Kim Jaeyeong Kim , Taehoon Lim Taehoon Lim , Inhwan Oh Inhwan Oh , Bupju Jeon Bupju Jeon , Ilhyun Jung Ilhyun Jung , Chul An Chul An
Published: October 2002

The relation between film quality and deposition rate of hydrogenated amorphous silicon films deposited by electron cyclotron resonance plasma chemical vapor deposition using H2/SiH4 has been investigated. The properties of amorphous silicon films were improved with increasing deposition rate; photoconductivity increased and optical band gap, full width at half maximum and the ratio of the concentration of dihydride to that of monohydride decreased. The high deposition rate was a very important factor to obtain high quality amorphous silicon films grown by electron cyclotron resonance plasma chemical vapor deposition using H2/SiH4.
Improvement in Electrical Properties at an n-GaAs/n-GaAs Regrown Interface Using Ammonium Sulfide Treatment
Authors: Furuhata Naoki , Shiraishi Yasushi
Published: October 2002

Electrical properties in an n-GaAs/n-GaAs interface regrown by molecular beam epitaxy (MBE) were remarkably improved using ammonium sulfide [(NH4)2S
x
] treatment prior to regrowth. Reflection high-energy electron diffraction observations indicate that GaAs native oxide is removed by this treatment at a 500°C substrate temperature. This is 100°C lower than the temperature for removal of a native oxide by conventional thermal annealing in MBE. Transmission line model measurement shows that contact resistance at the (NH4)2S
x
-treated interface is 1.8×10-6 Ωcm2, while it is 6.0×10-5 Ωcm2 without this treatment. Capacitance-voltage measurement and secondary-ion mass spectroscopy show that this reduction, in contact resistance at the regrown interface, is due to sulfur atoms in the interface behaving as donors (at a carrier concentration of 2×1018 cm-3); therefore, they compensate impurities such as carbon or oxygen in the interface. These results reveal that (NH4)2S
x
-treatment before regrowth is useful for improving device performances; that is, reducing source resistance for field-effect transistors fabricated by n+-GaAs selective growth.
Growth by the Flux Method and Transport Properties of Sr14-xCaxCu24O41 Single Crystals
Authors: Noji Takashi , Kakimoto Katsumi , Koike Yoji
Published: October 2002

Single crystals of Sr14-x
Ca
x
Cu24O41 with dimensions on the order of 1×0.05×1.5 mm3 (x=0) and 0.3×0.05×2 mm3 (x=6.8) have been grown using NaCl as a flux. Anisotropic properties of the electrical resistivity and the thermoelectric power of these single crystals have also been investigated.
Position Alignment in Algebraic Reconstruction Method by Using Center of Gravity
Authors: Tsuneta Ruriko , Nakamura Kuniyasu , Kakibayashi Hiroshi
Published: October 2002

The algebraic method was applied for transmission electron microscope (TEM) images taken from four directions. The reconstruction accuracy of this method was then evaluated for a 3-dimensional specimen structure. The reconstruction error was simulated by using various images which contain projection error, dark current noise, and position error. A 10% projection error and 20-dB dark current noise in the projection image resulted in reconstruction errors of 15% and 13%, respectively. On the other hand, the position error influence was so extreme that 58% reconstruction error was induced by displacement of only ±4-pixels between the projection images. It was found that a position alignment of images within ±1 pixel was necessary in order to achieve proper reconstruction. A new position alignment method using the center of gravity of a projection image is applied for TEM images of uranyl acetate. Using this alignment method, a 3-dimensional structure was successfully reconstructed from four images.
A Melnikov Method for Strongly Odd Nonlinear Oscillators
Authors: Ge Zheng-Ming , Ku Fu-Neng
Published: October 2002

In this paper, explicit calculations that extend the applicability of the Melnikov method to include strongly odd nonlinear and large forcing amplitude oscillating systems, are presented. We consider the response of the strongly nonlinear oscillating system governed by an equation of motion containing a parameter ε which need not be small. Phenomena considered are steady state response of strongly nonlinear oscillators subject to harmonic excitation. Two examples are given, they are the strongly nonlinear Duffing's equation and a pendulum suspended on a rotating arm. Finally, a adjustable factor is used to fit the simulation data. The theoretical chaotic behavior regions thus defined and plotted in the forcing amplitude versus parameter plane give the lower bounds for the true chaotic motion zones.
Trade-Off between Hot Carrier Effect and Current Driving Capability Due to Drain Contact Structures in Deep Submicron MOSFETs
Authors: Lee Sang-Gi , Lee Hi-Deok , Lee Young-Jong , Jeong Ju-Young , Eo Yungseon , Kwon Oh-Kyong , Lee Chang-Hyo
Published: October 2002

We, for the first time, have analyzed the contact structure dependent hot carrier effect in quarter-micron n-channel metal semiconductor field effect transistor (nMOSFETs). We measured the DC stressed current degradation characteristics, the substrate current characteristics, and the hot carrier induced photon emission characteristics of MOSFETs withW/L=20/0.25 microns having various contact structures. From experiments, we consistently observed that the degradation increases rapidly as the number of contact holes increases while current driving capability improves moderately. We also calculated the average electron temperature in devices with different contact structures from the energy distribution of emitted photons. The electron temperatures of 3- and 26-contact hole devices were about 4700 K and 6000 K, respectively. We have developed a HSPICE circuit model to simulate various contact structures. Both simulation and experimental results indicate that the current driving capability saturates at more than 5 contact holes of n-channel MOSFET withW/L=20/0.25 microns.
Deep-Submicron Single-Gate Complementary Metal Oxide Semiconductor (CMOS) Technology Using Channel Preamorphization
Authors: Miyake Masayasu , Kobayashi Toshio , Sakakibara Yutaka , Deguchi Kimiyoshi , Takahashi Mitsutoshi
Published: October 2002

Deep-submicron single-gate complementary metal oxide semiconductor (CMOS) technology using channel preamorphization (CP) is described. CP improves the short-channel behavior of nMOS as well as pMOS because sharp and shallow boron channel doping is achieved. CP also suppresses reverse short-channel effects in nMOS. Utilizing CP effectively, deep-submicron single-gate CMOS with good short-channel behavior has been fabricated.
Characteristics of New Poly-Si Thin Film Transistor with a-Si Channel Region Near the Source/Drain
Authors: Jeon Jae-Hong , Park Cheol-Min , Yoo Juhn-Suk , Kim Cheon-Hong , Han Min-Koo
Published: October 2002

We propose the new poly-Si TFT structure which reduces the leakage current effectively employing highly resistive a-Si region in the channel. This new device has selectively crystallized active layer, where both edges of channel region adjacent to source and drain are not crystallized and remain a-Si. In the proposed device, the amorphous silicon region behaves like an offset to reduce the leakage current and also acts as the conduction channel of carriers under the ON state, so that the ON-current can be maintained. The experimental results show that the ON/OFF current ratio of proposed device is 2.71×106 while that of conventional one is 2.67×105. In the fabrication of the proposed device, there are not any additional photomasking steps and mis-align problem.
A Unified Chemical Bonding Model for Defect Generation in a-SiH: Photo-Induced Defects in Photovoltaic Devices and Current-Induced Defects in TFTs
Authors: Yang Hong , Lucovsky Gerald
Published: October 2002

Generation of metastable neutral and charged defects in hydrogenated amorphous silicon (a-Si:H) by reactions involving changes in H-atom bonding arrangements has been studied by ab initio calculations applied to small molecules. A unified defect generation model has been developed in which reactions pathways for photo-induced defect generation in PV devices are initiated by hole-electron pair recombination and/or deep trapping, and in thin film transistor (TFT) devices by electron trapping. Reactions pathways are proposed for intrinsic processes involving only Si and H-atoms, as well as extrinsic processes involving O and NH impurities as well. In photovoltaic (PV) devices, defect generation includes the creation of neutral and charged defects and involves displacive rather than diffusive hydrogen motion, thereby ensuing metastability. The positively charged defects are associated with over-coordinated H-, O- and N-atoms. In TFT devices, defect generation results from electron trapping in anti-bonding orbitals of Si–H groups, and includes the formation of neutral and negatively charged Si-atom dangling bonds.
Evaluation of 0.3 µm Poly-Silicon CMOS Circuits for Intelligent Power IC Application
Authors: Matsudai Tomoko , Terauchi Mamoru , Yoshimi Makoto , Yasuhara Norio , Ushiku Yukihiro , Nakagawa Akio
Published: October 2002

In this paper, we report on the fine device performance of a 0.3 µm gate length polysilicon complementary metal-oxide-semiconductor (CMOS). The breakdown voltage of 0.3 µm n-channel metal-oxide-semiconductor field effect transistor (NMOSFET) devices exceeds 6 V, which is higher than that of NMOSFET devices on separation by implanted oxygen (SIMOX) wafer. The drain current of a 10 µm channel width device is 540 µA, which is one-fifth of that of NMOSFET on SIMOX. The leakage current is less than 10-11 A/µm, when the gate voltage is below 0 V. The S-factor is 125 mV/dec, and the threshold voltage is 0.4 V. Therefore the ON/OFF current ratio is greater than 107. A delay time of 1 ns is achieved in polysilicon NAND rings. Hence, it is ascertained that the polysilicon CMOS is applicable for the fabrication of control and protection circuits on power devices.
Highly Reliable SiO2 Films Formed by UV-O2 Oxidation
Authors: Teramoto Akinobu , Kobayashi Kiyoteru , Ohno Yoshikazu , Hirayama Makoto
Published: October 2002

We have developed and evaluated SiO2 films formed in a dry oxygen ambient at 600–900°C under ultraviolet irradiation (UV-O2 oxidation). It has been found that the constant current time-dependent-dielectric-breakdown (TDDB), stress induced leakage current and the hole-trapping characteristics of SiO2 films formed by the UV-O2 oxidation at 900°C, are superior to those formed by the conventional dry oxidation. The TDDB lifetime of the SiO2 films formed by the UV-O2 oxidation at 600°C is also longer than that formed by the conventional dry oxidation at 900°C and wet oxidation at 600°C. These facts indicate that the highly reliable gate oxide is realized by the UV-O2 oxidation. The UV-O2 oxidation technology is very useful for the production of future devices which require low-temperature processing.
Dominant Factor for the Concentration of Phosphorus Introduced by Vapor Phase Doping (VPD)
Authors: Sato Tsutomu , Mizushima Ichiro , Aoki Nobutoshi , Tsunashima Yoshitaka
Published: October 2002

The dominant factor for the surface concentration of n-type impurity, introduced by vapor phase doping technique using phosphine, was investigated and the possibility of a high surface concentration was pursued. It was found that the surface concentration of phosphorus could be controlled dominantly by the PH3 partial pressure. It was confirmed that the phosphorus atoms adsorb on the surface of the silicon substrate throughout the doping process. A new diffusion model via the adsorption layer at the surface is proposed. Electrically active phosphorus with a surface concentration as high as 8×1019 atoms/cm3 was successfully obtained.
Performance Characteristics of Jet-type Generator of Singlet Oxygen for Supersonic Chemical Oxygen-Iodine Laser*1
Authors: Jarmila Kodymová Jarmila Kodymová , Otomar Špalek Otomar Špalek
Published: October 2002

A jet-type singlet oxygen generator based on a gas-liquid chemical reaction yielding singlet oxygen, O2(1
Δ
g), for pumping the supersonic chemical oxygen-iodine laser was investigated. In addition to O2(1
Δ
g) and residual chlorine concentrations, a content of water formed during O2(1
Δ
g) generation was estimated (because of its detrimental effect on lasing) in gas flowing from the generator to the laser active region. The experimental conditions were determined under which an effect of liquid droplets escaping from the generator was negligible, and accordingly, a content of water vapour was suppressed to a value corresponding to the saturated water vapour pressure. It was also proved that a reduction in the relative water content, and a consequent increase in the laser output power, could be achieved by increasing peroxide and hydroxide concentration in the generator liquid, and by decreasing a liquid temperature and a total pressure in the generator.
Precipitation of Boron in Highly Boron-Doped Silicon
Authors: Mizushima Ichiro , Mitani Yuichiro , Koike Mitsuo , Yoshiki Masahiko , Tomita Mitsuhiro , Kambayashi Sigeru
Published: October 2002

The clustering of boron in highly boron-doped silicon and its influence on electrical deactivation are reported. Highly boron-doped crystalline silicon was fabricated as a starting material by solid phase epitaxy of boron-doped amorphous silicon films. Boron can be supersaturated in the crystallized samples annealed at a low temperature of about 600°C. A lot of precipitates, containing clustered boron, were observed in the samples annealed at high temperatures of about 1000°C. The chemical states and the atomic configuration of boron in samples annealed at various temperatures corresponded to the electrical deactivation of boron.