bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Dependence of Jc for F-Doped Hg1223 Filament
Authors: Tomoko Goto Tomoko Goto , Kazuo Watanabe Kazuo Watanabe , Satoshi Awaji Satoshi Awaji
Published: October 2002

A superconducting F-doped Hg
x
Ba2Ca2Cu3Re0.2O
y
filament was produced by a two-step method. The precursor Ba2Ca2Cu3Re0.2O
x
filament was fabricated using a solution spinning method and reacted in an evacuated fused quartz tube with a pellet of Hg1Ba1.8Ca2Cu3Re0.2(BaF2)0.2O
x
. The influence of fluorine on the transport J
c of the F-doped Hg1223 filament at 77 K was examined in magnetic fields of up to 10 T. F-doping resulted in a formation of dense liquidus texture and marked improvement in the field dependence of J
c for the filament. A J
c of more than 102 A/cm2 was maintained at 77 K in a field of 10 T.
Confirmation of AlGaAs Crystal Domain Inversion Using Asymmetric Wet Etching and Optical Second-Harmonic Generation Methods
Authors: Xu Chang-Qing , Takemasa Keizo , Nakamura Koji , Wada Hiroshi , Takamori Takeshi , Hideaki Okayama Hideaki Okayama , Takeshi Kamijoh Takeshi Kamijoh
Published: October 2002

The occurrence of crystal domain inversion on a (001) GaAs substrate was confirmed by a direct observation method based on asymmetric wet etching of AlGaAs and an optical method based on second-harmonic generation. Direct evidence of crystalline inversion was exhibited in samples with a periodic structure prepared by wafer bonding, selective removal of the bonded GaAs, and metal-organic vapor phase epitaxial regrowth on the patterned template.
Phase Transition in the Molecular Crystal Structure of Langmuir-Blodgett Film Containing Pyrrole: Molecular Mechanics Simulations
Authors: Shiratori Seimei Sha , Takesi Nishikawa Takesi Nishikawa , Kohei Yokoi Kohei Yokoi
Published: October 2002

We studied, by atomic force microscopy (AFM), the changes in the molecular arrangement of arachidic acid ( C20) Langmuir-Blodgett (LB) film with increasing quantity of pyrrole (Py) molecules which we used as spacer molecules for C20 molecules in the LB film. When the concentration of Py molecules in the C20 LB film was increased from 0% to 150%, the crystal structure of the LB film changed as follows: oblique lattice→hexagonal lattice→square lattice. These observations agreed qualitatively with the results of computer simulation based on molecular mechanics. Precise control of the crystal structure of LB film by adjusting the number of spacer molecules such as Py in the LB film is possible.
Electrical Properties of AlGaAs/GaAs Two-Dimensional Electron Gases (2DEGs) Grown on GaAs Substrates Cleaned by an Electron Cyclotron Resonance (ECR) Hydrogen Plasma
Authors: Naoto Kondo Naoto Kondo
Published: October 2002

AlGaAs/GaAs two-dimensional electron gases (2DEGs) are grown on GaAs substrates by molecular beam epitaxy (MBE) with various thicknesses of GaAs buffer layers. Prior to the growth, the substrates are cleaned using an electron cyclotron resonance (ECR) hydrogen plasma at low temperatures where native oxides are not removed from the surface by heating alone. The electrical properties of 2DEGs are evaluated using van der Pauw and Hall effect measurements. The sheet carrier densities and electron mobilities of the plasma-cleaned samples with more than 20-nm-thick buffer layers exhibit almost the same properties as the sample with a 600-nm-thick buffer layer at 77 K. ECR hydrogen plasma cleaning is found to be a promising technique for the regrowth process.
High-Power, High-Efficiency GaInP/AlGaInP Laser Diode
Authors: Pekka Savolainen Pekka Savolainen , Markus Pessa Markus Pessa
Published: October 2002

We report on high-power ridge-waveguide GaInP/AlGaInP laser diodes emitting at the wavelength of 670 nm. These lasers, processed into 40×1,200 µ m2 shallow ridge waveguide structures, with anti-reflection/high-reflection mirror coatings exhibit the c
w output powers in excess of 1.25 W, when mounted p-side down on heat sinks. The maximum power is limited by the catastrophic optical damage at the front facet. When mounted p-side up, the maximum c
w power is about 1 W, which is thermally limited. The thermal roll-over tests show that the lasers are very robust.
Preparation of ZnO/Au Nanocomposite Thin Films by Electrodeposition
Authors: Yoshino Takako , Takanezawa Susumu , Takashi Ohmori Takashi Ohmori , Hideki Masuda Hideki Masuda
Published: October 2002

ZnO/Au nanocomposite thin films were fabricated by electrodepositon from an aqueous solution of Zn(NO3)2 and KAuCl4. The composite film contained small particles of Au, the average diameter of which was in the range of 18 to 25 nm. The composite films were transparent and were red due to surface plasmon absorption of small Au particles deposited without subsequent heat treatment.
Room-Temperature Synthesis of Crystallized Luminescent SrMoO4 Film by Active Electrochemical Dissolution of Molybdenum
Authors: Woo-Seok Cho Woo-Seok Cho , Masahiro Yoshimura Masahiro Yoshimura
Published: October 2002

Crystallized luminescent SrMoO4 film has been prepared on a molybdenum substrate in an alkaline solution containing strontium ions by active electrochemical dissolution of molybdenum at room temperature (25° C). The film showed only a single green emission at 536 nm with an excitation wavelength of 285 nm at liquid nitrogen temperature (-196° C), strongly suggesting that it consisted of well-crystallized defect-free crystals.
Terahertz Emission Study of Femtosecond Time-Transient Nonequilibrium State in Optically Excited YBa 2Cu 3O 7-δ Thin Films
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 observed the temperature dependence of a femtosecond time-transient photoresponse in YBa2Cu3O7-δ thin films by detecting terahertz (THz) emission. Ultrashort electromagnetic pulses which are referred to as THz emission were generated by ultrafast supercurrent modulation with femtosecond laser pulse irradiation. The transient response is discussed in relation to the quasiparticle dynamics of the nonequilibrium superconductor.
Optically Controlled Metal-Oxide Semiconductor Field-Effect Transistor Operated by Long-Wavelength Light
Authors: Tomonari Yamagata Tomonari Yamagata , Kazuhiko Shimomura Kazuhiko Shimomura
Published: October 2002

The drain-to-source current of a metal-oxide semiconductor field-effect transistor (MOSFET) was controlled by long-wavelength laser light for the first time. The device studied was composed of an absorption region and a MOSFET, and these two regions were bonded by polyimide. When the voltage was applied to the absorption region, it showed the normal operation of a MOSFET. When the laser light with a wavelength of 1.48 µm was irradiated on to the absorption region, a responsivity of more than 100 A/W was achieved. This device modulates the current of the MOSFET by changing the electric field in the absorption region, and it has the possibility of high-speed operation up to 60 GHz.
A Method for Calculating Momentum Matrix Elements with Pseudopotentials
Authors: Hiroyuki Kageshima Hiroyuki Kageshima , Kenji Shiraishi Kenji Shiraishi
Published: October 2002

A convenient method for calculating momentum matrix elements with pseudopotentials is proposed. To eliminate errors due to poor representation by the pseudopotentials of the atomic core region, a core-repair term is introduced. This approach is very efficient, especially for the separable-type pseudopotentials, to reduce computational time. It is also applicable to non-norm-conserving ultrasoft pseudopotentials as well as general norm-conserving pseudopotentials. Therefore, various optical properties can be calculated easily with this approach.
Novel Microstructures Prepared by the Mixed Langmuir-Blodgett Technique and Identified by Atomic Force Microscopy
Authors: Hai-Ming Wu Hai-Ming Wu , Shou-Jun Xiao Shou-Jun Xiao
Published: October 2002

Array like domain structures were prepared in the mixed monolayer films composed of fatty acid and 5, 10, 15-triphenyl-20-(4-dl-α-phenylalanylamindo)phenyl porphyrin (TPPP) and investigated by atomic force microscopy (AFM). The mixtures exhibit the fatty acid domains in the liquid-condensed (LS) state on the condition of long alkyl chain. By shortening the length of the hydrocarbon chain, TPPP domains in the liquid-expanded (LE) state occur in the mixed monolayer films.
Unstable Region of Solid Composition in Ternary Nitride Alloys Grown by Metalorganic Vapor-Phase Epitaxy
Authors: Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

A chemical equilibrium model is applied to analyze the growth of AlGaN, InGaN and InAlN alloys using metalorganic vapor-phase epitaxy (MOVPE). The vapor-solid distribution relationship and the phase diagram for deposition are calculated. It is shown that unstable regions of solid composition exist in InGaN and InAlN alloys. The origin of the unstable region is also discussed.
Theoretical Study of the Surface Reaction Mechanism of GaN with HCl
Authors: Okamoto Yasuharu , Toshikazu Takada Toshikazu Takada , Yuji Mochizuki Yuji Mochizuki
Published: October 2002

Ab initio molecular orbital calculations are performed to investigate the three successive surface reactions of GaN with HCl. These reactions correspond to the simplest model which accounts for GaN chemical etching by HCl. We observed two characteristic points about these reactions. First, all of these reactions are exothermic and the reaction energies are about 20–29 kcal/mol. Second, the activation energy of the reaction decreases as the number of Ga–Cl bonds increases. The calculation shows that the first reaction of the GaN surface with HCl is the rate-determining one and the calculated reaction barrier is less than 10 kcal/mol.
Optical Observation of Single-Electron Charging Effect at Room Temperature
Authors: Uehara Yoichi , Ohyama Sadauki , Kimihiko Ito Kimihiko Ito , Sukekatsu Ushioda Sukekatsu Ushioda
Published: October 2002

By optical spectroscopy we have observed the single-electron charging effect of a small Au particle at room temperature. The high energy cut-off \hbarω max of visible light emitted by a sample under a scanning tunneling microscope (STM) is ordinarily equal to e
V
0 where V
0 is the tip-sample bias voltage. However, when the electron is injected into a small Au particle (diameter ∼6 nm) that is quasi-isolated on a thin insulator layer, the cut-off energy shifts below e
V
0. The physics that underlies the observed optical effect is common with that of previously observed Coulomb blockade and Coulomb staircase.
In-plane Observations of RF-sputtered LiNbO3 Thin Films Using an Energy Dispersive Total-Reflection X-Ray Diffractometer*1
Authors: Nishida Takashi , Ishida Kenji , Horiuchi Toshihisa , Tadashi Shiosaki Tadashi Shiosaki , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

“In-plane” structures of RF-magnetron sputtered LiNbO3 thin films grown on Pt(111)/ SiO2/Si and α- Al2O3(001) substrates have been observed using a newly developed energy dispersive total-reflection X-ray diffractometer (ED-TXRD). Clear diffractions from both the LiNbO3 thin films and substrates, with low background level, could be obtained using the ED-TXRD. Hence, it was possible to precisely determine orientations and in-plane lattice spacings within the epitaxially grown thin films. In the case of α- Al2O3(001) single crystalline substrates, the rocking curves for in-plane orientation of the grown LiNbO3 film could be analyzed with high angular resolution. Moreover, it was found that the lattice spacings (d-spacings) of the LiNbO3 films grown on the Pt(111)/ SiO2/Si substrates were slightly larger than those of LiNbO3 bulk crystals. From the measurement results using both the ED-TXRD and surface profilometry, the occurrence of residual stresses and lattice defects in the films and substrates were discussed.
Visible Light Emission from SiOx Films Synthesized by Laser Ablation
Authors: Tetsuya Makimura Tetsuya Makimura , Yasuhiko Kunii Yasuhiko Kunii , Naoto Ono Naoto Ono , Kouichi Murakami Kouichi Murakami
Published: October 2002

We have developed a method for synthesizing SiOx films with visible light emission, applying a laser ablation technique. The films were formed by depositing laser-ablated silicon particles in oxygen gas diluted with helium gas. Soft X-ray absorption spectroscopy revealed that the composition of the film is controlled by the total pressure of the gas. Films with particular composition exhibit intense red photoluminescence with a peak below 1.5 eV after annealing in argon gas at 1000°C. In addition to this, most of the films exhibit 2.2-eV photoluminescence after annealing at 500°C. On the basis of these results, the origin of the photoluminescence is discussed.
Super Photon Generator Using Collisions of Circulating Relativistic Electrons and Wire Targets
Authors: Yamada Hironari
Published: October 2002

A simple method for generating brilliant X-ray beams is proposed, in which inelastic collisions of circulating relativistic electrons with a thin wire target are used. The high brilliance of this new photon source results from narrow angular divergence due to the kinematics of relativistic electrons, and repeated use of electron beams. The estimated brilliance of this source based on a 50 MeV electron storage ring exceeds that of compact synchrotron light sources in the hard X-ray region.
Soft-Magnetic Properties of Nanocrystalline Fe-Zr-B-Ni Bulk Alloy Produced by Warm Extrusion
Authors: Kojima Akinori , Makino Akihiro , Kawamura Yoshihito , Akihisa Inoue Akihisa Inoue , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: October 2002

Magnetic properties of nanocrystalline Fe90-
x

Zr7B3Ni

x

( x=2–4) melt-spun ribbons and consolidated bulk alloys have been investigated. The magnetostriction of Fe90-
x

Zr7B3Ni

x

ribbon changed from -1.8×10-6 to 1.8×10-6 when x changed from 0 to 4 and became zero at x=1.5. Soft-magnetic properties of ribbon and consolidated bulk Fe90-
x

Zr7B3Ni

x

were better than those of Fe90Zr7B3. Nanocrystalline Fe86Zr7B3Ni4 consolidated bulk with grain sizes of 10–20 nm exhibited magnetic flux density of 1.55 T, maximum permeability of 23000, effective permeability of 3360 at 300 Hz, and coercivity of 14 A/m.
A Lateral Insulated Gate Bipolar Transistor Structure with the Collector-Short Region for Improved Latch-Up Performance
Authors: Hitoshi Sumida Hitoshi Sumida , Atsuo Hirabayashi Atsuo Hirabayashi
Published: October 2002

This letter describes the collector-short technique for improving latch-up performance without an increase in the on-state voltage for the lateral insulated gate bipolar transistor (LIGBT). The concept of our proposed technique is to prevent the injection of the minority carrier, which induces the latch-up, at the sharp corner of the emitter region, where the minority carrier concentrates. This can be done by replacing the p+-collector layer at the sharp corner of the emitter region with the n+-collector-short layer. Experimental results show that the latch-up current of the LIGBT with the collector-short region is 1.5 times higher than that of the LIGBT without the collector-short region, while there is no difference in the on-state voltage of the LIGBTs.
A New Homologous Series of Superconducting Cuprates with the 22(n-1)n Structure, (Hg1-xTlx)2Ba2Can-1CunOy (x∼0.4, n = 3, 4)
Authors: Tatsuki Tadashi , Tokiwa-Yamamoto Ayako , Fukuoka Atsushi , Tamura Toshiyuki , Wu Xiao-Jing , Moriwaki Yoshiyuki , Usami Ryo , Adachi Seiji , Keiichi Tanabe Keiichi Tanabe , Shoji Tanaka Shoji Tanaka
Published: October 2002

A new homologous series of superconducting cuprates containing a mercury-based bilayer has been synthesized using a high-pressure, high-temperature technique. It is found that Tl doping stabilizes a bilayer block with the rock-salt structure i.e. (Hg1-
x

Tl

x

)2–O2. (Hg1-
x

Tl

x

)2Ba2Ca2Cu3O

y

and (Hg1-
x

Tl

x

)2Ba2Ca3Cu4O

y

as-prepared samples with analized Tl contents of approximately 0.4 exhibited bulk superconductivity below 45 K and 114 K, respectively.
Bi-Substituted Iron Garnet Films for Stable Faraday Rotation against Wavelength Variation in the 1.3 µm Band
Authors: Suzuki Toshiyasu , Hirotaka Kawai Hirotaka Kawai , Hiromitsu Umezawa Hiromitsu Umezawa
Published: October 2002

We report on the finding of a Bi-substituted Sm-containing iron garnet film ( La0.08Sm2.15Bi0.77Fe5O12) that realizes a high Faraday rotation stability against wavelength variation in the 1.3 µm band. This stability resulted from the peaks in the Faraday rotation at 1.24 µm and 1.38 µm due to Sm3+ ions. We calculated that such isolators could provide a 60 nm bandwidth in which the isolation would be maintained at 35 dB or higher. In addition, we discussed the relationship between the bandwidth and film composition.
NMR Study of Sm2Co17-xBx Compounds
Authors: Maruyama Fumio , Nagai Hiroyuki , Amako Yasushi , Adachi Hiroshi Yoshie
Published: October 2002

The contribution of the B atom to the magnetic properties of Sm2Co17-
x

B

x

for 0≤x≤1 is studied by means of NMR and magnetic measurements. The c-axis anisotropy was strengthened on adding B. The Co moment increased for 0≤x≤0.5 and decreased for 0.5≤x≤1. The 59Co NMR results show that the moment of Co close to B decreased more than that of Co far from B. For 0≤x≤0.5 the Co orbital moments µ orb increased except for Co at the 9d site, and µ orb of Co at the 18f site increased greatly. Thus the Co atom at the 18f site contributes greatly to strengthening of the axial anisotropy.
Relationship between Crystalline Defects and Wear of Natural Diamonds
Authors: Nishimura Kazuhito , Yoshinaga Hirotoshi , Ikawa Naoya , Hiraki Akoi
Published: October 2002

It has been clearly shown that the micro-fracture strength of a diamond is determined by the type and density of the intrinsic defects in the diamond's crystalline structure. In this study, cathodoluminescence (CL) was used as a non-destructive method of evaluating the micro-strength of raw diamonds in order to observe a natural diamond which had been thermally etched in plasma. It was confirmed that the etched structure and the CL structure were closely correlated, and it was clearly demonstrated that the preferentially etched parts were 2.46 eV zero-phonon line emission centers at which isolated substitutional nitrogen was present. From these results, CL was concluded to be a useful method of obtaining information for the design of diamond ultraprecision cutting tools.
Preferred Orientations of NiO Films Prepared by Plasma-Enhanced Metalorganic Chemical Vapor Deposition
Authors: Fujii Eiji , Tomozawa Atsushi , Hideo Torii Hideo Torii , Ryoichi Takayama Ryoichi Takayama
Published: October 2002

Thin films of nickel oxide (NiO) with NaCl-type structure were prepared on glass substrates at 400°C by plasma-enhanced metalorganic chemical vapor deposition using nickel acetylacetonate as a source material. The relationship between O2 flow rate, and preferred orientation and microstructure of the NiO films was investigated. Highly crystalline NiO film with (111) orientation was obtained at O2 flow rates as low as 3 cm3/min. As the O2 flow rate increased from 3 to 70 cm3/min, the orientation of NiO films changed from (111) to (100) and deposition rate decreased from 17 to 11 nm/min. Films with both (111) and (100) orientation had columnar structure. The origin of the preferred orientation of the NiO films was discussed.
A New Method of Surface Plasmon Excitation Mediated by Metallic Nanoparticles
Authors: Hayashi Shinji , Kume Tetsuji , Teruhiko Amano Teruhiko Amano , Keiichi Yamamoto Keiichi Yamamoto
Published: October 2002

A new method for exciting surface plasmon polaritons (SPP's) on a metal surface without using a prism coupler is experimentally tested. The method uses a layer of metallic nanoparticles placed on the metal surface. A thin layer of SiO2 containing Ag nanoparticles of average size ∼4 nm was deposited onto an Al thin film and light was incident directly onto the sample surface. The excitation of SPP's at the Al-overlayer interface was verified by the observation of a hollow light cone decoupled with the aid of a hemispherical prism, which was brought into contact with the sample. It was found that effective SPP excitation is possible when the Ag particles are placed very close to the Al surface (within ∼3 nm of the surface).
Orientation of Ni–Cr Thin Films with an Underlying Ti Layer
Authors: Nakamura Atsuko Iida
Published: October 2002

Insertion of a Ti thin film between an 80 wt% Ni–20 wt% Cr thin film and a glass-coated Al2O3 substrate resulted in a strongly (111) preferred orientation in the Ni–Cr thin film, which was deposited on the Ti layer by continuous sputtering. The preferred orientation and the cross section were observed by X-ray diffractometer (XRD) and high-resolution transmission electron microscopy (RRTEM), respectively. The Ni–Cr thin film was found to have a columnar structure and the column axes were normal to the substrate. In addition, the (111) orientation of Ni–Cr was observed to be almost parallel to the (100) orientation of Ti.
Dynamic Simulation of Redeposition of Backscattered and Sputtered Particles on Tungsten Irradiated by Plasmas
Authors: Ohya Jun Kawata
Published: October 2002

Redeposition of backscattered and sputtered particles due to their ionization and gyromotion in the scrape-off layer (SOL) is investigated using a dynamic simulation model of interaction of Maxwellian carbon ions with a tungsten surface. The implantation of projectile carbon ions during their bombardment causes reduction in the amounts of sputtered tungsten and backscattered carbon ions, and it causes an additional sputtering of carbon. Due to redeposition of emitted particles on the surface, the sputtering of tungsten (implanted carbon) is more (less) suppressed. Furthermore, a thick carbon layer is deposited on the tungsten surface at high SOL plasma temperatures, at which the surface is eroded if no redeposition is included in the simulation.
Photoinduced Hole Injection Multiplication in p-Type Quinacridone Pigment Films
Authors: Hiramoto Masahiro , Shuji Kawase Shuji Kawase , Masaaki Yokoyama Masaaki Yokoyama
Published: October 2002

A large photocurrent multiplication due to hole injection reaching 2500-fold was observed in organic p-type quinacridone pigment films. This phenomenon was revealed to be due to photoinduced excess hole injection from a positively biased metal electrode to the p-type organic film through its depletion layer under a high electric field, which is built up by the photo-accumulation of trapped electrons near the interface. This is a clear example that the reverse mechanism to the photoinduced electron injection observed for n-type organic pigment film can occur in p-type organic pigment film.
DC Superconducting Quantum Interference Devices with BiSrCaCuO Bicrystal Grain Boundary Junctions at 77 K
Authors: Takami Tetsuya , Kuroda Ken'ichi , Tanimura Junji , Kojima Kazuyoshi , Hirota Masahiro Nunoshita
Published: October 2002

We have developed dc superconducting quantum interference devices (SQUIDs) with grain boundary junctions of a BiSrCaCuO (BSCCO) thin film on a SrTiO3 (100) bicrystal substrate with a misorientation angle of 36.8°. The T
c and J
c of the BSCCO film were 93 K and 3×105 A/cm2 at 77 K, respectively. These SQUIDs operated at 77 K. The I-V characteristics of the SQUIDs were of resistively shunted junction (RSJ) type. A SQUID with 20-µ m-wide junctions showed Fraunhofer-like flux-voltage characteristics. The I
0
R
n product and the modulation voltage of a SQUID with 10-µ m-wide junctions were 23 µ V and 6 µ V at 77 K, respectively. The flux noise measured in a flux-locked loop mode was 2.0×10-5Φ0/ Hz0.5 in the white noise region.
120 mW High-Power Low-Noise GaAlAs Multiple-Quantum-Well Laser Diodes with a New Real Refractive Index Guided Self-Aligned Structure
Authors: Takayama Toru , Imafuji Osamu , Hashimoto Tadaro , Yuri Masaaki , Akio Yoshikawa Akio Yoshikawa , Kunio Itoh Kunio Itoh
Published: October 2002

We developed, for the first time, a new high-power, low-noise laser with power over 120 mW by using a multiple-quantum-well (MQW) real refractive index guided self-aligned (RISA) structure with a very low refractive index step. The lasers showed relative intensity noise level of less than -135 dB/Hz with 10% optical feedback in a wide output power range from 3 mW to 18 mW. Stable operation for over 1000 hours at 50° C with 35 mW was also achieved.
Nanometer-Scale Wires of Monolayer Height Alkanethiols on AlGaAs/GaAs Heterostructures by Selective Chemisorption
Authors: Akio Nagahara Hirotaka Ohno , Shangjr Gwo Shangjr Gwo , Wataru Mizutani Wataru Mizutani , Hiroshi Tokumoto Hiroshi Tokumoto
Published: October 2002

Self-assembled nanometer-scale wires (SANWs) composed of octadecylthiol [ODT, CH3(CH2)17SH] have been selectively formed on the GaAs surface of an AlGaAs/GaAs heterostructure. The sample grown by metal organic chemical vapor deposition (MOCVD) was cleaved to expose the AlGaAs/GaAs heterostructure in a solution containing the ODT molecules. Both surface properties and morphology of these wires have been investigated simultaneously by scanning probe microscopy. SANWs as narrow as 10 nm in width and ∼1.0 nm in height were observed. The inability to form an ODT monolayer on the AlGaAs surface was attributed to the formation of an oxide layer.
Molecular Beam Epitaxy of CuGaSe 2 on GaAs Substrate Using Metalorganic Copper and Gallium Precursors
Authors: Sho Shirakata Sho Shirakata , Kazuhisa Tamura Kazuhisa Tamura , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

The metalorganic molecular beam epitaxial growth of CuGaSe2 layers on a GaAs(100) substrate has been performed at 600°C using cyclopentadienylcoppertriethylphosphine (CpCuTEP), triethylgallium (TEGa) and selenium as source precursors. The CuGaSe2/GaAs layers have been grown under the systematically changing TEGa partial pressure. X-ray diffraction, photoluminescence (PL) and photoreflectance measurements have been carried out for the layers, and the CuGaSe2 layer grown under the optimum condition exhibited an exciton emission in the PL spectrum.
Heteroepitaxial Growth of α-Fe 2O 3 Thin Films on (111) GGG
Authors: Manabu Gomi Manabu Gomi , Hiroshi Toyoshima Hiroshi Toyoshima
Published: October 2002

Thin films of α-Fe2O3 have been prepared on gadolinium gallium garnet (GGG) (111) substrates by rf sputtering and subsequent heat treatment. The films deposited below 180°C and annealed at 900°C were found to exhibit a strong [0006] texture perpendicular to the film plane. X-ray pole figure analysis showed that a nearly single-crystalline film of (0001) α-Fe2O3 was grown on (111) GGG with an in-plane alignment of α-Fe2O3 [2*BAR*1*BAR**BAR*1*BAR*0] parallel to GGG [1*BAR*1*BAR*0]. Thus, the α-Fe2O3 films with the corundum crystal structure may be a promising buffer layer for achieving heteroepitaxy of various ferrite thin films onto a common substrate of GGG.
Blue-Green Photoluminescence from Ultrafine Colloidal Si Particles in 2-Propanol
Authors: Shingo Iwasaki Shingo Iwasaki , Takashi Ida Takashi Ida , Keisaku Kimura Keisaku Kimura
Published: October 2002

We have prepared Si nanocolloids by trapping Si ultrafine particles (UFPs) prepared by gas evaporation into an organic solvent. The average diameter of the Si UFPs is 4.8 nm. Strong blue-green photoluminescence (PL) from the Si UFPs has been observed at room temperature. The peak energy of the broad PL band is about 2.5 eV. We have investigated the dependence of the PL intensity on the aging of the sample and the average diameter of the Si particles.
Preparation of GaS Thin Films by Molecular Beam Epitaxy
Authors: Hiroyuki Yamada Hiroyuki Yamada , Keiji Ueno Keiji Ueno , Atsushi Koma Atsushi Koma
Published: October 2002

Layered semiconductor GaS thin films have been grown by molecular beam epitaxy on hydrogen-terminated Si(111) and GaSe(0001) substrates. Elemental sulfur is so volatile that we used a valved cell as a sulfur source. Two∼100 monolayer of GaS films were obtained which have sharp reflection high-energy electron diffraction (RHEED) patterns. The GaS thin film grown on GaSe(0001) was a single-domain one, whereas that on hydrogen-terminated Si(111) was a multidomain one. Both films have been proved to be stoichiometric and to have the same electronic structure as that of the bulk GaS.
Homoepitaxial Diamond Synthesis by DC Arc Plasma Jet Chemical Vapor Deposition
Authors: Akira Higa Akira Higa , Akimitsu Hatta Akimitsu Hatta , Toshimichi Ito Toshimichi Ito , Takehiro Maehama Takehiro Maehama , Minoru Toguchi Minoru Toguchi , Akio Hiraki Akio Hiraki
Published: October 2002

Homoepitaxial diamond films have been synthesized on (100) substrates by DC arc plasma jet chemical vapor deposition. It was shown that fabrication of epitaxial film with a smooth surface is possible at an appropriate substrate temperature T
s with methane and carbon dioxide concentrations of 1% each. At T
s ≥930°C, pyramidal hillocks form on the surface of the film, and irregular grain particles appear. However, if the methane concentrations are raised, even when substrate temperature is high, epitaxial films with smooth surfaces are formed. Epitaxial diamond film with a smooth surface shows much stronger cathodoluminescence than the film with pyramidal hillocks. From the results of the X-ray double-crystal analysis, the crystallinity of the epitaxial diamond layer is higher than or equal to that of the substrate of high-pressure-synthesized diamond. These results indicate that synthesis of high quality diamond film at a high growth rate, by DC arc plasma jet CVD, is possible.
Formation of Fluorocarbon Monolayers on Anodized Aluminium Plates by Vapor Phase Chemical Adsorption Technique
Authors: Soga Mamoru , Ikuta Shigeo , Ozaki Shinji , Ogawa Kazufumi
Published: October 2002

3,3,3-(Trifluoropropyl)trichlorosilane (TFPS) was deposited on anodized aluminium plates by a vapor phase chemical adsorption technique in order to form fluorocarbon monolayers. The monolayers from the TFPS vapor showed the same water-repellent property as the monolayers from the TFPS solution. The vapor phase chemical adsorption technique may enable the formation of monolayers from organic trichlorosilanes on plastics which are soluble or swollen in organic solvents.
Preparation of Fluorocarbon Multilayers by a Chemical Adsorption Technique
Authors: Ogawa Mamoru Soga
Published: October 2002

Preparing fluorocarbon multilayers by chemical adsorption or self-assembly was investigated. 1,10-Bis (trichlorosilyl) dodecafluorodecane (bis-trichlorosilane) was chemically adsorbed on aluminum coated glass plates in nonaqueous solution. The plates were washed with chloroform and deionized water, and then dried. The electrical properties of the multilayers, such as capacitance, tan
δ, leak current, and breakdown voltage were evaluated. The capacitance measurements imply that the multilayers of the bis-trichlorosilane molecules can be formed by repeating the chemical adsorption process.
Fabrication of a Nanometer-Scale GaAs Ridge Structure with a 92-MHz Anode-Coupled Reactive Ion Etcher Using Cl2/N2 Mixed Plasmas
Authors: Tadashi Saitoh Tadashi Saitoh , Hiroshi Kanbe Hiroshi Kanbe
Published: October 2002

A vertical etch profile of GaAs is achieved at a low bias voltage with a 92-MHz anode-coupled reactive ion etcher using chlorine-nitrogen plasmas. The added nitrogen gas not only dilutes the concentration of reactive chlorine radicals in the plasma also plays an important role in the vertical etching of GaAs. XPS analysis reveals no sidewall passivation by nitrogen. Reactive ion etching with a Cl2/N2 mixed plasma was used to fabricate ultra-fine GaAs patterns with a nanometer-scale ridge structure having a cross-section 15-nm wide by 150-nm high.
Fundamental Performance Limit of Integrated Systems
Authors: Yuji Okuto Yuji Okuto
Published: October 2002

The performance limits of integrated digital systems in terms of the functional throughput have been evaluated using the uncertainty principle and the thermal limit. Parallel processing capability and the limited power dissipation for each system were used as parameters. It is shown that, while the operation is limited by the uncertainty principle, the maximum obtainable functional throughput increases by increasing the degree of parallel processing through increasing the switching time of elemental switches to reduce their switching power. It is also shown that, while the operation is thermally limited, the expected maximum functional throughput is independent of switching speed so long as sufficient parallel processing is realized.
Light Scattering by Submicron Particles on Film–Coated Wafers
Authors: Hideyuki Kondo Hideyuki Kondo , Shigenari Yanagi Shigenari Yanagi , Kazushige Takaishi Kazushige Takaishi , Takayuki Shingyouji Takayuki Shingyouji , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

The intensity of light scattered by particles on film–coated wafers was measured as a function of film thickness using two types of particle counter with different optical configurations. The scattered light intensity was found to oscillate periodically with film thickness; the period of oscillation was in agreement with that of the reflectivity of the incident beam, and significant enhancement of scattering intensity was observed for thicknesses less than about 0.3 µm.
Bi-2212/Ag Superconducting Insert Magnet for High Magnetic Field Generation over 22 T
Authors: Okada Michiya , Tanaka Kazuhide , Fukushima Keiji , Sato Junichi , Kitaguchi Hitoshi , Kumakura Hiroaki , Kiyoshi Tsukasa , Inoue Kiyoshi , Togano Kazumasa
Published: October 2002

A superconducting insert magnet using Bi-2212/Ag multifilamentary tapes for high magnetic field generation has been successfully fabricated. The coil was made by a wind and react process and included a stack of four double pancakes. The dimensions of the stacked coil were 55 mm in height, 49 mm in outer diameter and 12.5 mm in clear core. The coil was inserted in a 21 T-class superconducting magnet and tested various backup fields at 4.2 K. The maximum magnetic field at the center B
0 of the coil reached 1.76 T under a backup magnetic field of 21 T, i.e., the magnetic field generated by the superconducting magnet system reached 22.8 T. The critical current density J
c of the Bi-2212 core and the coil current density J
c -coil reached 951 A/mm2 and 128 A/mm2 respectively. These J
c values are high enough for high field magnet applications such as 1 GHz-class NMR magnet.
GaOH: Unstable Species Liberated from GaAs Surface Oxides during Atomic Hydrogen Cleaning
Authors: Masamichi Yamada Masamichi Yamada
Published: October 2002

A mass spectroscopic study was carried out on atomic hydrogen ( H•) cleaning of GaAs substrates. During the H•-induced removal of surface Ga oxides at 410° C, a desorption of GaOH was observed along with a weak desorption of Ga2O. Upon interrupting the H• generation, the GaOH desorption stopped immediately, whereas the Ga2O desorption continued, indicating that the surface GaOH has a short lifetime. Considering the fact that bulk GaOH is unstable and has not yet been isolated, it is noteworthy that GaOH is a major desorption product of the reaction between H• and Ga oxides.
Ferrite Plating of Fe 3O 4 Films on Expanded Polytetrafluoroethylene Modified by Xe Excimer Lamp
Authors: Qun Zhang Qun Zhang , Manabu Gomi Manabu Gomi , Tomoyuki Itoh Tomoyuki Itoh , Masanori Abe Masanori Abe
Published: October 2002

Surface modification of expanded polytetrafluoroethylene (PTFE) from hydrophobic to hydrophilic by Xe excimer lamp irradiation is performed in order to enhance the adhesion of ferrite-plated films onto the PTFE. The contact angle of water droplet is about 60° before irradiation and decreases to 5° after irradiation. It is found that under the same ferrite plating condition, with increase of irradiation time, many more Fe3O4 nucleation sites are formed due to the increase of the number of OH groups on the PTFE caused by Xe excimer lamp irradiation photomodification.
Role of SiH4 Gas Heating in the Growth of Hydrogenated Microcrystalline Silicon
Authors: Takeshi Arai Takeshi Arai , Hajime Shirai Hajime Shirai
Published: October 2002

The effect of SiH4 source gas heating on the early stage of growth of hydrogenated microcrystalline silicon (µ c-Si : H) by plasma-enhanced chemical vapor deposition (PECVD) from SiH4 and H2 has been investigated to improve the film crystallinity and inhomogeneities. The crystallinity is improved without increasing the surface roughness on thermally grown SiO2 when the cathode temperature, T
c, is greater than 500° C. The major role of SiH4 gas heating is not only to increase the temperature of the growing surface but also to the thermally activate the deposition precursors on the growing surface and/or to generate polymerized precursors in the gas phase.
In Situ Monitoring of the Chemisorption of Hydrogen Atoms on (001) GaAs Surface in GaAs Atomic Layer Epitaxy
Authors: Koukitu Akinori , Taki Tetsuya , Naoyuki Takahashi Naoyuki Takahashi , Hisashi Seki Hisashi Seki
Published: October 2002

We study the chemisorption of hydrogen atoms on the (001) GaAs surface in an atmospheric pressure halogen transport ALE using the surface photoabsorption (SPA) method. The dependence of the SPA signal on the H2 partial pressure on the (001) Ga surface is investigated at 450° C. Furthermore, the Ga surface is monitored using temperature-programmed desorption (TPD) with SPA. It is shown that hydrogen in the carrier gas reacts dissociatively with Ga atoms on the (001) surface, and the desorption of hydrogen occurs by the reverse reaction in the inert carrier gas. The occurrence of these reactions is confirmed by the Langmuir equation of the dissociative isotherm.
Dependence of Rotation Speeds of Ultrasonic Quartz Motor on Length in Z-Axis Direction
Authors: Yoshida Takashi Aoki
Published: October 2002

Rotation speeds of an ultrasonic motor composed of a quartz rectangular parallelepiped cut perpendicular to the X, Y and Z axes were determined as a function of length in the Z-axis direction. It was found that unrotatable quartz becomes rotatable quartz without changing the frequency for the rotation by slightly trimming the length in the Z-axis direction.
Possibility of Growing High Quality Very Thin Single CdTe Crystals Directly on Mica
Authors: Shojiro Takeyama Shojiro Takeyama
Published: October 2002

Very thin CdTe crystals were grown on cleaved surfaces of (001)-mica (muscovite) substrate by a hot wall technique, and zincblende-type single-crystal films oriented on the (110)-plane were obtained. The thickness of the film investigated here is about 300 nm. Films obtained under optimized growth conditions exhibited a sharp exciton absorption line at low temperatures, showing that the crystal was of high quality. This fact may result from a new type of growth owing to ionic characteristics at the surface of the (001)-mica substrate. Analysis by atomic force microscopy revealed an extremely smooth surface with a root-mean-square roughness of 2 nm over a 1 µ m2 area.
Dynamic Formation of Excited Helicon Wave Structure and Estimation of Wave Energy Flux Distribution
Authors: Shunjiro Shinohara Shunjiro Shinohara , Yoko Miyauchi Yoko Miyauchi , Yoshinobu Kawai Yoshinobu Kawai
Published: October 2002

Dynamic changes in helicon wave structure, due to excitation by a helical antenna, are investigated as a function of time. Before a density jump (steep density increase), not a propagating wave but a standing wave near the antenna is found. After the jump, a selective helicon wave excitation of azimuthal mode numbers m = 1 and m = - 1 is demonstrated, and the first the energy flux estimate shows different axial profiles for the two modes.
Layer-by-Layer Growth of GaN on GaAs Substrates by Alternate Supply of GaCl3 and NH3
Authors: Tsuchiya Harutoshi , Akamatsu Manabu , Masahiko Ishida Masahiko Ishida , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

Atomic layer epitaxy (ALE) of GaN on GaAs substrates was tried by alternate supply of GaCl3 and NH3, and the growth process was analyzed by the surface photo-absorption (SPA) method. When the GaN layers were grown on GaAs surface at 500° C, typical SPA signals indicating the layer-by-layer growths were observed. Change in the reflection intensity (SPA signal) after the GaCl3 supply for the GaN growth was much slower than that of GaAs. This result indicates that the reaction between GaCl3 and N or NH3 was much slower than that between GaCl3 and As or AsH3. The crystallinity of GaN grown on (001) GaAs was almost amorphous. On the other hand, the GaN grown on (111) GaAs had a wurtzite structure and was a single crystal.
ArF-Excimer-Laser-Assisted Highly Selective Etching of InGaAs/InAlAs Using HBr and F2 Gas Mixture
Authors: Takazawa Hiroyuki , Shinichiro Takatani Shinichiro Takatani , Seiji Yamamoto Seiji Yamamoto
Published: October 2002

Highly selective etching of InGaAs/InAlAs was achieved by irradiation with a 193-nm ArF excimer laser in a HBr and F2 atmosphere. Adding F2 gas to the HBr gas enhanced the InGaAs etching rate while reducing the InAlAs etching rate, resulting in an etching rate ratio of over 450. The etching mechanism is discussed in terms of pressure dependence and laser fluence dependence data. Our findings suggest that ArF-excimer-laser-assisted etching is feasible for gate-recess etching of InGaAs/InAlAs field effect transistors.
Photopumped Stimulated Emission from Homoepitaxial GaN Grown on Bulk GaN Prepared by Sublimation Method
Authors: Satoshi Kurai Satoshi Kurai , Yoshiki Naoi Yoshiki Naoi , Toshimitsu Abe Toshimitsu Abe , Susumu Ohmi Susumu Ohmi , Shiro Sakai Shiro Sakai
Published: October 2002

We have observed stimulated emission at room temperature from a photopumped homoepitaxial GaN for the first time. A homoepitaxial layer was grown by atmospheric metalorganic chemical vapor deposition (MOCVD) on small hexagonal bulk GaN prepared by the sublimation method. The lasing threshold of the pumping power density is 0.86 MW/cm2 and the stimulated emission is polarized with its electric vector perpendicular to the c-axis.
Giant Electric Field Effect on Al/BaTiO 3/(Y 0.6Pr 0.4)Ba 2Cu 3Oy Structures
Authors: address:hontsu@info.waka.kindai.ac.jp Shigeki Hontsu \footnoteE-mail , Hitoshi Tabata Hitoshi Tabata , Masaya Nakamori Masaya Nakamori , Junya Ishii Junya Ishii , Tomoji Kawai Tomoji Kawai
Published: October 2002

Planar metal-ferroelectric-superconductor field effect transistors (MFS-FETs) have been fabricated on SrTiO3 (100) substrates. The FET has the structure of Al/BaTiO3 (BTO) /(Y0.6Pr0.4)Ba2Cu3Oy (YPBCO), where the oxide layers are grown heteroepitaxially by ArF excimer laser deposition using an in situ metal mask changing system. The relative dielectric constant (ε
r) of BTO is 200 at 77 K, and the ferroelectric field effects at low temperature have been measured. The source-drain current (I
SD) is enhanced 28% by applying negative gate voltage of -1.5 V. These results indicate that the Al/BTO/YPBCO structures are favorable for use in the superconducting FET.
Magnetically Excited Plasma Oxidation of GaAs
Authors: Ryuichi Nakamura Ryuichi Nakamura , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Relatively good-quality oxide of GaAs was grown using magnetically excited oxygen plasma (helicon wave) with substrate heating (300°C) or a mixture of Ar gas in oxygen. Post-thermal annealing at 400°C in oxygen substantially improved the capacitance-voltage ( C–V) characteristics, which showed very small frequency dispersion without hysteresis. However, no inversion behavior was observed. X-ray photoelectron spectroscopic measurements showed that As2O3 and Ga2O3 are the main component species of these oxides.
Characterization and Improvement of GaAs Layers Grown on Si Using an Ultrathin a-Si Film as a Buffer Layer
Authors: Hao Maosheng , Shao Chunlin , Soga Tetsuo , Jimbo Takashi , Umeno Masayoshi , Liang Junwu , Zheng Lianxi , Xiao Zhibo , Xiao Jianfei
Published: October 2002

GaAs epilayers grown on Si by metalorganic chemical vapor deposition (MOCVD) using an ultrathin a-Si buffer layer were characterized by deep-level transient spectroscopy (DLTS). Six electron traps with activation energies of 0.79, 0.67, 0.61, 0.55, 0.53 and 0.32 eV below the conduction band were determined by fitting the experimental spectra. Two of the levels, C (0.61 eV) and F (0.32 eV), were first detected in GaAs epilayers on Si and identified as the metastable defects M3 and M4, respectively. In order to improve the quality of GaAs/Si epilayers, another GaAs layer was grown on the GaAs/Si epilayers grown using MOCVD. The deep levels in this regrown GaAs epilayer were also studied using DLTS. Only the EL2 level was found in the regrown GaAs epilayers. These results show that the quality of the GaAs epilayer was greatly improved by applying this growth process.
Electrical Properties of 100 nm Pitch Cr/Au Fine Electrodes with 40 nm Width on GaInAs
Authors: Hiroo Hongo Hiroo Hongo , Hiroaki Tanaka Hiroaki Tanaka , Yasuyuki Miyamoto Yasuyuki Miyamoto , Toshihiko Otake Toshihiko Otake , Jiroo Yoshinaga Jiroo Yoshinaga , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

The electrical properties of Cr/Au electrodes with fine-pitch and small contact area are reported. Using three wire electrodes of 100 nm-pitch, 20 nm thickness, 4 µm length and 40 nm width, contact currents through the metal-semiconductor junction with area of 40 nm ×500 nm were measured. The current passing through each metal wire was measured to show the connection of the wire. The contact size dependence of the current characteristics was also investigated. As the contact size is reduced, the contact resistance per area at 0 V was found to increase.
Time-Resolved Studies of Ion Desorption from Ca Surfaces Using Double-Pulsed Laser Ablation Technique
Authors: Nishikawa Hiroaki , Szabo Gabor , Tomoji Kawai Tomoji Kawai
Published: October 2002

We have performed double-pulsed laser ablation experiments on Ca samples with an ArF excimer laser. The amount of desorbed monovalent ions was measured using a quadrupole mass spectrometer as a function of the delay between the laser pulses. In the case of 6 ns delay, the total amount of desorbed ions is decreased to ≈0.1 times that with no delay. On the basis of this result, it is discussed that the laser ablation of Ca metal is caused by multiphoton photochemical reaction via a lattice/defect-assisted mechanism.
All-Solid-State Mirror-Dispersion-Controlled Sub-10 fs Ti:Sapphire Laser
Authors: Yamakawa Koichi , Aoyama Makoto , Spielmann Tamitake Itoh
Published: October 2002

We report what is to our knowledge the first use of a frequency-doubled cw diode-pumped solid-state laser to pump a mirror-dispersion-controlled Ti:sapphire laser. Stable, sub-10 fs duration pulses, with output powers of ∼230 mW, were obtained for a pump power of ∼4 W. The system (including the pump laser) fits on a 1.2×0.6 m optical breadboard.
Compact Ar–Xe Discharge Laser with Surface Multichannel Arc Ultraviolet Preionizer
Authors: Takao Komi Takao Komi , Kiyoshi Yatsui Kiyoshi Yatsui
Published: October 2002

Highly efficient, compact Ar–Xe lasers preionized using surface multichannel arc (SMA) ultraviolet (UV) radiation have been successfully developed to improve overall efficiency. We present that the overall efficiency can be enhanced by decreasing the specific input energy. When the specific input energy was 2.7 J/ l, an overall efficiency of 2.5% was achieved. The saturation parameter and the small-signal gain are estimated by fitting Rigrod's equation to the results of laser output power versus reflectivity of the output coupler. The kinetics of laser oscillation were considered in terms of the temporal laser intensity of the individual oscillation lines during multioscillation.