bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of Volume Wave Plasma with Internally Mounted Cylindrical Planar Microwave Launcher and Two-Dimensional Field Analysis Using Finite Difference Time Domain Method
Authors: Ogino Akihisa , Naito Katsutoshi , Terashita Fumie , Nanko Shohei , Nagatsu Masaaki
Published: July 2005

In this paper, we presented experimental results on the production of volume wave plasma (VWP) using an internally mounted cylindrical planar microwave launcher, for application to novel plasma processings, such as inner wall coating, impurity-free etching or internal sterilization of medical instruments using VWP. It was demonstrated that the ellipsoidal VWP is produced in front of a microwave launcher in He or Ar gas atmosphere. Numerical analyses of microwave fields radiated from a planar launcher have been carried out using the two-dimensional finite difference time domain (FDTD) method to determine the mechanism of VWP production in middle of the chamber. It was shown that the calculation results showed fairly good agreements with the experimental results measured using a dipole antenna probe. The spatial distributions of plasma density and the temperature of VWP were also measured using a double probe. It was found that the electron density is comparable to or slightly less than cutoff density of 7.4 ×1010 cm-3 corresponding to the microwave frequency of f
m=2.45 GHz, and that the electron temperature is approximately 6 eV at the plasma center.
Highly Ordered Nanopatterning of DNA with 40 nm Diameter Using Anodic Porous Alumina Substrate
Authors: Matsumoto Futoshi , Kamiyama Momoka , Nishio Kazuyuki , Masuda Hideki
Published: July 2005

The patterning of single-stranded DNA with a pattern period of 63 nm and a pattern diameter of 40 nm is successfully demonstrated using a gold disk array formed on a highly ordered anodic porous alumina substrate. The formation of DNA patterns is confirmed indirectly by observation of adsorbed streptavidin-coated colloidal Au particles as markers of DNA fixation. Thus, it is demonstrated that nanopatterning of DNA can be achieved using inexpensive equipment and conventional techniques. The present process allows for complete control of the size and periodicity of the Au disk array, which enables the formation of a highly regular arrangement of nanometer-sized patterns of biological molecules.
Si Nano-Photodiode with a Surface Plasmon Antenna
Authors: Ishi Tsutomu , Fujikata Junichi , Makita Kikuo , Baba Toshio , Ohashi Keishi
Published: July 2005

Nano-photodiodes with a subwavelength active area using the optical near-field enhanced by surface plasmon resonance are proposed. We fabricated a Si Schottky photodiode that consists of an active area of 300 nm in diameter and a surface plasmon antenna to generate the carrier within the active area efficiently. The fabricated photodiode shows an increase of the photocurrent by several tenfold compared to that without a surface plasmon antenna. This result suggests an enhanced photogeneration of carriers in a semiconductor via surface plasmon resonance. Such a Si nano-photodiode is a potential high-speed optical signal detector because the opto-electronic conversion process occurs within a subwavelength scale.
Micromachined Thermoelectric Hydrogen Sensor of Double-Membrane Structure
Authors: Tajima Kazuki , Choi Yeongsoo , Shin Woosuck , Izu Noriya , Matsubara Ichiro , Murayama Norimitsu
Published: July 2005

We have prepared a noble micromachined gas sensor by combining two identical micro-hot plates on membranes fabricated by anisotropic wet etching of silicon substrate and a thermoelectric hydrogen sensor. The thermoelectric hydrogen sensor selectively detects the hydrogen gas working with the thermoelectric effect of SiGe thin film and the Pt-catalyzed exothermic reaction of hydrogen oxidation. The double-membrane structure thermally isolates two central and rectangular membranes from the rim of a room-temperature bulk substrate, minimizing offset voltage by keeping both membranes at the same temperature. The Pt catalyst as small as 1.5 ×1.5 mm2 builds up the temperature difference in the thermoelectric film by the oxidation of 1% hydrogen in air, producing an output voltage of 0.38 mV as a signal at an operating temperature of 100°C.
Magnetic Alignment of Nonmagnetic Mica Crystals Achieved at Low Field Intensity Due to High Concentration of Paramagnetic Ions
Authors: Uyeda Chiaki , Takashima Ryoichi , Hiraoka Kensuke
Published: July 2005

Magnetic alignments of micron-sized mica dispersed in ethanol were achieved at low field intensity when concentrations of paramagnetic ions were high. Alignments were caused mainly by paramagnetic anisotropy, according to Δχ-T relationships obtained from single-crystal measurements. The field for full orientation B
S observed for biotite microcrystals, which had a paramagnetic susceptibility of χPARA=4.4 ×10-5 emu/g, was B
S=0.21 kOe at T=300 K; B
S was 0.6 kOe for muscovite microcrystals with χPARA= 4.8 ×10-6 emu/g (T=300 K). Alignments have not been observed at such low fields for nonferromagnetic oxide particles. B
S was previously measured to be 36 kOe for diamagnetic phlogopite. Biotite and phlogopite have almost equivalent crystal structures and possess similar diamagnetic anisotropy; biotite should hence have a B
S value similar to that of phlogopite if its paramagnetic anisotropy is not strong.
Violation of Bell's Inequality in 1550 nm Band without Subtraction of Accidental Coincidences
Authors: Yoshizawa Akio , Tsuchida Hidemi
Published: July 2005

A violation of Bell's inequalities using quantum entanglement indicates the nonlocality of two particles such as photons and electrons. We observe a violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality, a particular Bell's inequality, in polarization-entangled photon pairs in the 1550 nm band. For photon pair generation based on spontaneous parametric down conversion, a fiber-optic two-photon interferometer with two periodically poled lithium niobate waveguides is adopted. The obtained S value of the CHSH inequality is 2.44 ±0.02 without subtraction of accidental coincidences, yielding a violation by ∼22 standard deviations in an hour. Two-photon interference with a visibility of 0.885 is also observed. If those coincidences are subtracted, the visibility becomes almost unity.
Fatigueless Ferroelectric Capacitors with Ruthenium Bottom and Top Electrodes Formed by Metalorganic Chemical Vapor Deposition
Authors: Furukawa Taisuke , Kuroiwa Takeharu , Fujisaki Yoshihisa , Sato Takehiko , Ishiwara Hiroshi
Published: July 2005

Ferroelectric Ru/Bi4-x
La
x
Ti3O12/Ru capacitors were fabricated by combining metalorganic chemical vapor deposition (MOCVD) of top and bottom Ru electrodes and spin-coating of the ferroelectric film. After optimization of the deposition conditions, good ferroelectric properties (2P
r=18 µC/cm2, P
r: remanent polarization) and low leakage current density (2×10-6 A/cm2) were achieved. No significant fatigue phenomenon (decrease of P
r) was observed even after 1010 switching cycles.
Characteristics of Very High Frequency Plasma Produced with Ladder-Shaped Electrode at High Pressure
Authors: Takatsuka Hiromu , Yamauchi Yasuhiro , Takeuchi Yoshiaki , Mashima Hiroshi , Yamashita Hideaki , Kawai Yoshinobu
Published: July 2005

A very high frequency (VHF) plasma was produced with a ladder-shaped electrode at high pressure and plasma parameters such as the density and temperature of electrons were measured as a function of pressure using a Langmuir probe. A VHF power source with a frequency of 60 MHz was used and the power was up to 450 W. When the pressure was increased from 0.3 Torr to 4 Torr, the plasma density decreased at high pressure, while the electron temperature was approximately 10 eV at high pressure. Furthermore, Langmuir probe characteristics indicated that there exist many negative ions at high pressure.
Molecular Weight Dependence of Phase Behavior in Side-Chain Liquid Crystalline Polymer Which Exhibits Reentrant Nematic Phase
Authors: Tomikawa Naoki , Itoh Tomomichi , Okazaki Yusuke , Adachi Mitsu-aki , Tokita Masatoshi , Watanabe Junji
Published: July 2005

We prepared poly(6-[4-(4'-cyanophenyl)phenoxy]hexyl acrylate)s with various molecular weights (M
n) and narrow molecular weight distributions, and examined the M
n dependence of phase behavior which includes the reentrant nematic (RN) phase. Polymers with M
n lower than 20,000 form nematic (N), smectic A (SmA) and RN phases as temperature decreases, while ones with M
n higher than 20,000 form only N phase. The disappearance of SmA in longer chains is caused by the decrease in N-SmA temperature and the increase of SmA-RN one with increasing M
n. Result indicates that the polymer length is one of the significant factors affecting the reentrant behavior in side-chain liquid crystalline (LC) polymers.
Characterization of Field Emission from Nano-Scale Diamond Tip Arrays
Authors: Yamada Takatoshi , Hwang Doo-Sup , Vinod Purayath Robert , Makino Toshiharu , Fujimori Naoji
Published: July 2005

Nano-scale diamond tip arrays on single crystals (100) are fabricated by plasma etching and their field emission characteristics are studied. We fabricate three types of structures: ordered tips with a high density, ordered tips with a low density and an unordered whisker structure. In field emission measurements, the ordered tips with a low density have better field emission than the ordered tips with a high density and the unordered whisker structure. Field enhancement factors are estimated from Fowler-Nordheim plots (βFN) and tip geometry (βtip). Although the βFN is almost the same as the βtip for the ordered tips with a low density, the βFNs of the ordered tips with a high density and the unordered whisker structure are one order smaller than the βtips. This indicates that using a tip array with a low density helps in reducing the neighboring shielding effects, thereby leading to βFN similar to βtip. We found experimentally that the tip arrangement plays an important role in the field emission from diamond.
Formation of Nanorod-Shaped Surface of C60 Film and Its Field Emission Properties
Authors: Fujii Akihiko , Mizukami Hiroyoshi , Hiwatashi Shinji , Araki Hisashi , Ozaki Masanori , Yoshino Katsumi
Published: July 2005

The surface morphology of C60 films fabricated by vacuum deposition was modified by a spin-cast treatment process with various organic solvents and a nanorod-shaped surface was obtained in the case of spin-cast treatment with trans-1,2-dichloroethylene. The field emission properties of C60 films, the surfaces of which were modified, were found to depend on their surface morphology.
Analysis of Layer Structure Variation of Periodic Porous Silicon Multilayer
Authors: Maehama Takehiro , Teruya Tatsuji , Moriyama Yuki , Sonegawa Tomihiro , Higa Akira , Toguchi Minoru
Published: July 2005

Structures of periodic porous silicon multilayer, which were formed by the current density modulation method, were investigated by cross-sectional scanning electron microscopy (SEM) observation. When the layers were formed with a current density of 20 mA/cm2 or less the thickness of the layers was constant regardless of the stack position of the layer. When the layers were formed with a current density of 50 mA/cm2 or more, the thickness of the layers decreased and the porosity of the layers increased as the stack position of the layer became deep. The layer peeled off when the porosity of the layer increased up to aproximately 100%. The thickness variation of the layers and the peeling were prevented by raising the temperature of the electrolyte.
Synthesis of Multiwalled Carbon Nanotubes at Temperatures below 300°C by Hot-Filament Assisted Chemical Vapor Deposition
Authors: Ishikawa Yutaka , Jinbo Hironobu
Published: July 2005

Synthesis of multiwalled carbon nanotubes was attempted at low temperatures by chemical vapor deposition using a hot filament. Ethanol was used as a carbon source. As a catalyst, particles produced by scratching a cobalt plate with sandpaper were mixed with zeolite powder. We successfully synthesized multiwalled carbon nanotubes at 280°C. The diameter of the nanotubes was in the range of 8–20 nm. The reaction was carried out at atmospheric pressure, therefore we did not use a vacuum pump in the synthesis. We also did not use inflammable and explosive gas. Thus, we have succeeded in synthesizing multiwalled carbon nanotubes at low temperatures using very simple and low-risk equipment.
Synthesis of Metallic Iridium Oxide Nanowires via Metal Organic Chemical Vapor Deposition
Authors: Zhang Fengyan , Barrowcliff Robert , Stecker Greg , Pan Wei , Wang Deli , Hsu Sheng-Teng
Published: July 2005

Iridium oxide (IrO2) nanowires with diameters of 10 to 50 nm and length of 1 to 2 microns were synthesized using Metal Organic Chemical Vapor Deposition (MOCVD) with (methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I) as the precursor on Si or SiO2 substrate with and without metal nanoparticles as catalysts. Scanning electron microscopy (SEM) and low-resolution transmission electron microscopy (LRTEM) studies show very uniform nanowires diameters and high-resolution (HR) TEM image and electron diffraction pattern reveal single crystal IrO2 nanowires having rutile structure with the growth direction along <001>. HRTEM studies further indicate that the IrO2 nanowires were grown via vapor-solid mechanism having naturally formed sharp tips. It was found that a thin layer of metal film on Si substrate, such as Au, Ti, Ni, and Co, facilitate IrO2 nanowires synthesis and selective growth of IrO2 nanowires on substrate was realized. The IrO2 nanowires are metallic conductive using titanium as contact without annealing. The ability to grow single crystal metallic IrO2 nanowires opens up novel opportunities in vacuum electronics, nanoelectronics, field emission and display applications.
Zn1-xCdxO/ZnO Heterostructures for Visible Light Emitting Devices
Authors: Nakamura Atsushi , Ishihara Junji , Shigemori Satoshi , Yamamoto Kenji , Aoki Toru , Gotoh Hideki , Temmyo Jiro
Published: July 2005

Wurtzite Zn1-x
Cd
x
O/ZnO heterostructures were successfully grown by remote plasma enhanced metalorganic chemical vapor deposition (RPE-MOCVD) and were investigated by photoluminescence (PL) spectroscopy. The flatness of Zn1-x
Cd
x
O films was investigated by an atomic force microscope (AFM), indicating the typical RMS value of 0.5 nm. The optical properties of the Zn0.96Cd0.04O film were characterized by micro-PL at 4 K, exhibiting micro-structural and positional uniformities in the films. In the double heterostructure consisting of ZnO/Zn0.92Cd0.08O/ZnO, temperature and excitation intensity dependencies of PL spectra were examined. The PL emission is characterized as localized and free exciton emission. A dependence with a slope near unity is obtained from the excitation dependence of the PL intensity. Blue-green emission (2.78 eV) was demonstrated from the double-heterostructure at room temperature.
Characteristics of Organic Light-Emitting Devices by the Surface Treatment of Indium Tin Oxide Surfaces Using Atmospheric Pressure Plasmas
Authors: Jeong Chang Hyun , Lee June Hee , Lee Yong Hyuk , Cho Nam Gil , Lim Jong Tae , Moon Cheol Hee , Yeom Geun Young
Published: July 2005

This study examined the effects of a He/O2 and He/SF6 atmospheric pressure plasma surface treatment of indium tin oxide (ITO) glass on the ITO surface and electrical characteristics of organic light emitting diodes (OLEDs). The OLEDs composed of ITO glass/2-TNATA/NPD/Alq3/LiF/Al showed better electrical characteristics, such as lower turn-on voltage, higher power efficiency, etc., after the He/O2 or He/SF6 plasma treatment. The He/SF6 treatment resulted in superior electrical characteristics compared with the He/O2 treatment. The electrical improvement as a result of the He/SF6 and He/O2 plasma treatments is related to the decrease in the carbon and Sn4+ concentration on the ITO surface and fluorine doping of the ITO possibly indicating a change in the work function as a result of the treatments.
Effect of Plasticization of Poly(Vinyl Cinnamate) on Liquid Crystal Orientation Stability
Authors: Sung Shi-Joon , Cho Ki-Yun , Hah Hyundae , Lee Seongnam , Park Jung-Ki
Published: July 2005

A cinnamate group is a well-known compound group used in the dimerization reaction by ultraviolet irradiation, and cinnamate polymers are studied as photoalignment materials. In this study, the radical reaction of cinnamate side groups attached to a flexible polymer backbone is considered feasible using thermal energy. To induce the thermal reaction of cinnamate side groups, we modified the flexibility of poly(vinyl cinnamate) by introducing a plasticizer into the polymers and investigated the thermal reaction behavior of cinnamate side groups. The plasticization of poly(vinyl cinnamate) makes the induction of the thermal reaction of cinnamate side groups easier than that of unmodified poly(vinyl cinnamate). The thermal reaction of cinnamate side groups is closely related to the enhancement of the thermal stability of the liquid crystal orientation of polymer films with polarized UV irradiation.
Electrical and Chemical Properties of Photo-Cross-Linked Polymeric Insulating Materials
Authors: Kim Gi Heon , Yoon Sung-Min , Kim Chul Am , Suh Kyung Soo
Published: July 2005

Photosensitive polymeric insulating films, which were prepared by mixing host polymers and a photosensitizer, exhibit high chemical resistance and excellent electrical properties. These polymer films formed by the spin-coating method were exposed through a mask to patterned radiation of UV light. The nonexposed areas of these films were dissolved by an appropriate solvent. Leakage current densities for these films are very low, approximately 5 ×10-7 ∼3 ×10-8 A/cm2 at a bias of 10.0 V. These polymer insulators are particularly suitable for plastic-based electronic device applications.
355-nm UV Light Generation in High-Quality CsB3O5 Fabricated by Post-Growth Heat Treatment
Authors: Saji Takashi , Yoshimura Masashi , Hisaminato Naoto , Mori Yusuke , Sasaki Takatomo , Katsura Tomoki , Kojima Tetsuo , Nishimae Junichi
Published: July 2005

Cesium triborate (CsB3O5) is expected to be an efficient harmonic generator in the UV region. However, as-grown single crystals of CsB3O5 often contain a high density of optical scattering centers that significantly reduce device performance. We found that these can be removed by a post-growth heat treatment with quenching. Treated crystals were employed for the third harmonic generation of a high-power Nd:YAG laser operating at 1064 nm. We generated high-power 355-nm output power of 14 W, which is three times higher than that obtained by a commercial LiB3O5 crystal under the same experimental conditions.
Production of Short-Lived Positron-Emitting Radioactive Nuclei Using a 2.4 TW, 50 fs Tabletop Laser
Authors: Takahashi Hironori , Okihara Shin-ichiro , Fujimoto Masatoshi , Ohsuka Shinji , Matsukado Koji , Okazaki Shigetoshi , Ito Toshiaki , Aoshima Shin-ichiro , Tsuchiya Yutaka
Published: July 2005

We produced a short-lived positron-emitting radioisotope 13N by using MeV-order deuterons emitted from relativistic laser plasma generated by a tabletop laser. For generation of the plasma, laser pulses with a peak power of 2.4 TW and a pulse duration of 50 fs were focused with a 10 Hz repetition rate onto a microporous polytetrafluoroethylene film loaded with deuterated polystyrene, where the maximum intensity at the focal point was 3 ×1018 W/cm2. The irradiation of melamine resins by deuterons for 55 s produced 13N of 1.00 ±014 Bq through a nuclear reaction of 12C(d,n)13N. This is the first report on an actual activation using a table-sized femtosecond laser.
Nanoholes in InP and C60 Layers on GaAs Substrates by Using AlGaAs Nanowire Templates
Authors: Tateno Kouta , Gotoh Hideki , Watanabe Yoshio
Published: July 2005

As one of the nano-scale fabrication techniques, free-standing nanowires are promising. We have developed a new method for nanohole fabrication using nanowire templates; that is, etching the exposed wires selectively after the layer growth. We have demonstrated nanoholed array in InP and C60 layers on GaAs substrates. For the metalorganic vapor phase epitaxy of InP, (111)B facets tend to form so that the AlGaAs nanowires are easily removed. Tilted nanowires and nanoholes are possible by using (311)B substrates. As another holed layer case, a C60 layer was tried. We found that this method can also be applied to the fragile material like C60.
Highest Density 1.3 µm InAs Quantum Dots Covered with Gradient Composition InGaAs Strain Reduced Layer Grown with an As2 Source Using Molecular Beam Epitaxy
Authors: Amano Takeru , Sugaya Takeyoshi , Komori Kazuhiro
Published: July 2005

We propose a GaAs-based 1.3 µm InAs quantum dot (QD) structure for optical devices that uses dimeric arsenic (As2) and a highly strained GaInAs cover layer. The characteristics of 1.3 µm InAs QDs that employ As2 are different from those of QDs that use As4. Our optimum structure exhibits the first room temperature emission of over 1.3 µm with a linewidth of 22 meV and a high density of over 1 ×1011 cm-2 using only a cover layer. We were also able to achieve a very high density of 3.3 ×1011 cm-2 and a full width at half mazimum of 23 meV for a triple-stack structure within the critical thickness. This result is promising as regards achieving an optical device with QDs of over 1.3 µm on a GaAs substrate for use in fiber communications.
Operation Characterization of Flash Memory with Silicon Nitride/Silicon Dioxide Stack Tunnel Dielectric
Authors: Lai Hsiang-Yueh , Chang-Liao Kuei-Shu , Wang Tien-Ko , Sung Chao-Feng
Published: July 2005

The operating characteristics of flash memory devices with tunnel dielectrics comprising a silicon nitride layer or a silicon nitride/silicon dioxide (N/O) stack and annealed at various temperatures are studied. The present work indicates that flash memory devices with an N/O stack tunnel dielectric have a higher program/erase speed and reliability than those with a single Si3N4 layer. The stack tunnel dielectric composed of a thick Si3N4 layer and a thin SiO2 layer exhibits even better performance for flash memory operation. Flash memory devices having N/O stack tunnel dielectrics annealed at low temperatures show better performance in terms of erase speed and charge retention but poor robustness under read disturbance.
Laser Thomson Scattering Measurements of Electron Density and Temperature Profiles of a Striated Plasma in a Plasma Display Panel (PDP)-Like Discharge
Authors: Hassaballa Safwat , Tomita Kentaro , Kim Young Kee , Uchino Kiichiro , Hatanaka Hidekazu , Kim Young Mo , Park Chung Hoo , Muraoka Katsunori
Published: July 2005

A laser Thomson scattering technique has been used to directly measure the electron density (n
e) and electron temperature (T
e) profiles of a striated plasma in a plasma display panel (PDP)-like discharge. A modulation in n
e was observed only on the anode side of an electrode substrate; this corresponds to a feature similar to that of the emission images obtained using an intensified charge-coupled device (ICCD) camera. Also, a modulation in T
e was observed and it was found to be out of phase from the modulation in n
e.
Micromachined Optical Near-Field Bow-Tie Antenna Probe with Integrated Electrostatic Actuator
Authors: Ono Takahito , Iwami Kentaro , Esashi Masayoshi
Published: July 2005

A bow-tie antenna structure consisting of two opposing metal electrodes separated by a narrow gap is fabricated with an integrated electrostatic actuator to allow the gap to be narrowed further. This configuration allows the near-field localization and conversion efficiency to be optimized beyond that achievable by direct fabrication. The structure is expected to represent an excellent near-field source for high-resolution imaging with high optical transmittance. Electrostatic actuation is demonstrated in both contact- and noncontact-mode operations, and near-field imaging is successfully performed using the device in the illumination mode.
InAsSb Quantum Dots Grown on GaAs Substrates by Molecular Beam Epitaxy
Authors: Kudo Makoto , Nakaoka Toshihiro , Iwamoto Satoshi , Arakawa Yasuhiko
Published: July 2005

InAsSb quantum dots were grown on GaAs substrates by two methods. One was grown by conventional molecular-beam epitaxy in which arsenic and antimony were irradiated simultaneously. The other was grown by irradiating previously grown InAs dots with antimony to prevent antimony flux from functioning as a surfactant. Although the photoluminescence spectrum of the dots grown by the conventional method had two peaks, the photoluminescence spectrum of the dots grown by the second method had a single peak. Peaks at wavelengths longer than 1.4 µm were observed in the photoluminescence spectrum of the InAsSb quantum dots grown by the second method.
Characteristics of 1.3 µm Laser Diode with Carbon-Doped InAlAs Layer
Authors: Kurihara Kaori , Arai Nobuhiro , Shimoyama Kenji
Published: July 2005

InAlGaAs-based laser diodes with carbon doping have been demonstrated. The epitaxial conditions of the carbon doping in InAlAs are critically limited in terms of reduction in oxygen contamination, when carbon concentration is increased. This limitation is more severe at high temperatures. We investigated the most appropriate growth conditions for reducing contamination and realized C-InAlAs with a carrier concentration of 1 ×1018 cm-3 even at a temperature as high as 618°C. We then fabricated a broad-stripe 1.3 µm laser with C-InAlAs and found that this laser shows optical characteristics superior to those with Zn-doped InAlAs.
Printed Carbon Nanotube Field Emitters for Backlight Applications
Authors: Kim Yong Churl , Yoo Eun Ho
Published: July 2005

A 5-inch diagonal parallel-gated backlight unit for a liquid crystal display (LCD) was fabricated using carbon nanotube (CNT) paste. A brightness of 10,000 cd/m2 was demonstrated at 10 KV of anode voltage, and 31 lm/W of light efficiency (for P-22 white phosphor) was obtained. We inserted a mesh electrode with appropriate apertures between anode and cathode plates, which suppressed charge-up effects on the exposed insulator surface and dark electron emission induced by the anode voltage. Such a simply structured backlight is expected to be cost-effective for applications in large-area LCD TVs.
Field Effect of Self-Assembled Organic Multilayer in Nanogap Electrode; Current Oscillation Behaviour at Room Temperature
Authors: Ishida Takao , Horikawa Masayo , Nakano Miki , Naitoh Yasuhisa , Miyake Koji , Mizutani Wataru
Published: July 2005

We have measured the field effect of the conductance of self-assembled multilayers of insulating alkylchain molecules in 20-nm-gap electrodes. We observed the field-induced currents at specific gate bias voltages and current oscillation behavior against gate bias voltage at room temperature. In addition, similar device characters were obtained with a high yield of more than 70%.
Patterned Magnetic Recording Media Using Anodic Porous Alumina with Single Domain Hole Configurations of 63 nm Hole Interval
Authors: Yasui Kenji , Morikawa Takuya , Nishio Kazuyuki , Masuda Hideki
Published: July 2005

Patterned magnetic recording media composed of the arrays of Co cylinders were fabricated using anodic porous alumina with single domain hole configuration. The ac electrodeposition of Co into the holes of the alumina matrix of 63 nm hole interval generated the arrays of Co cylinders with high aspect ratios. The structures and magnetic properties of the obtained patterned magnetic recording media are described. The magnetic recording properties were dependent on the geometrical structures of the Co cylinder arrays in the alumina matrix.
Measuring Molecular Conductivities Using Single Molecular-Sized Gap Junctions Fabricated without Using Electron Beam Lithography
Authors: Naitoh Yasuhisa , Liang Tien-Tzu , Azehara Hiroaki , Mizutani Wataru
Published: July 2005

We demonstrate a procedure for fabricating back-gate-type sub 5 nm gap junctions without using electron beam lithography. The fabricating procedure contains two photolithographic processes followed by shadow evaporation and oxygen plasma ashing. Oligo(para-phenylenevinylene) trimers (OPV3) attached to methylthiol at both ends were bridged between these junctions. The temperature dependence of OPV3 conductance indicated the characteristic behavior of hopping conduction. The results indicate that these junctions can be used in the study of conductance measurements through molecular wires.
AlGaN/GaN Heterostructure Field-Effect Transistors with Current Gain Cut-off Frequency of 152 GHz on Sapphire Substrates
Authors: Higashiwaki Masataka , Matsui Toshiaki
Published: July 2005

AlGaN/GaN heterostructure field-effect transistors (HFETs) with a gate length (L
G) of 60–250 nm were fabricated on a sapphire substrate. The HFET structure was grown by plasma-assisted molecular-beam epitaxy, and a 2-nm-thick SiN film was formed on the device surface by catalytic chemical vapor deposition. All of the HFETs showed outstanding DC device performance. They exhibited maximum drain current densities of 1.50–1.55 A/mm and extrinsic transconductances of 340–400 mS/mm. The 60-nm-gate HFET had a current gain cut-off frequency ( f
T) of 152 GHz and a maximum oscillation frequency ( f
max) of 173 GHz. To our knowledge, the f
T and f
max are the highest ever reported for GaN-based transistors. These superior high-frequency characteristics were achieved with a process using a thin and high-Al-content barrier layer, high-quality catalytic chemical vapor deposition (Cat-CVD) SiN passivation, and sub-0.1-µm gates defined by electron-beam lithography.
Milliwatt Power Deep Ultraviolet Light Emitting Diodes Grown on Silicon Carbide
Authors: Moe Craig G. , Masui Hisashi , Schmidt Mathew C. , Shen Likun , Moran Brendan , Newman Scott , Vampola Kenneth , Mates Tom , Keller Stacia , Speck James S. , DenBaars Steven P. , Hussel Chris , Emerson David
Published: July 2005

Deep ultraviolet light emitting diode structures with a peak wavelength of 275 nm were grown by metalorganic chemical vapor deposition on (0001) silicon carbide. Despite its strong ultraviolet light absorption, silicon carbide was chosen as a substrate rather than sapphire for its improved thermal conductivity and the potential for vertically conducting devices. An output power of 0.11 mW was observed at 300 mA DC during single device on-wafer testing, and output powers of 2.09 mW at 1.3 A were obtained from a packaged, silicone encapsulated array of five devices. Forward voltages as low as 4.9 V at 20 mA were obtained. The injection profile of Cp2Mg during the p-AlGaN blocking layer was instrumental in the suppression of emission at undesired wavelengths and the realization of peak-to-defect level ratios greater than 100.
Growth of Thick AlN Layer by Hydride Vapor Phase Epitaxy
Authors: Liu Yu-Huai , Tanabe Tomoaki , Miyake Hideto , Hiramatsu Kazumasa , Shibata Tomohiko , Tanaka Mutsuhiro , Masa Yoshihiko
Published: July 2005

Thick AlN crystals were grown by conventional hydride vapor phase epitaxy (HVPE) on AlN/sapphire templates under low pressure (∼15 Torr) at high temperature (1100°C–1200°C). Colorless, mirror-like AlN films were obtained at the growth rates of up to 20.6 µm/h. The best root mean square (RMS) value of atomic force microscope (AFM) observations for the AlN surface was 2.34 nm. The typical values of full width half maximum (FWHM) of X-ray rocking curves for (0002) and (1012) diffraction of AlN films were 173–314 arcsec and 1574–1905 arcsec, respectively. We also investigated the influences of carrier gas, growth temperature and growth rate on the crystal quality.
High Gain and High Sensitive Blue-Ultraviolet Avalanche Photodiodes (APDs) of ZnSSe n+-i-p Structure Molecular Beam Epitaxy (MBE) Grown on p-type GaAs Substrates
Authors: Abe Tomoki , Ando Koshi , Ikumi Katsushi , Maeta Hiroyasu , Naruse Junji , Miki Kouhei , Ehara Akihiro , Kasada Hirofumi
Published: July 2005

High gain and high sensitive blue-ultraviolet avalanche photodiodes (APDs) are developed using high quality ZnSSe n+-i-p hetero-structure grown on p-type GaAs substrates by molecular beam epitaxy (MBE). The short wavelength APDs have been realized by a new technique of interface superlattice buffers between p-GaAs and p-ZnSe hetero-interfaces, by which we have overcome large interface energy barriers (>1 eV: for hole-conduction) and unstable dark leakage currents. Utilizing a benefit of the n+-i-p structure on p-GaAs, the short wavelength APDs have been designed with an thin transparent n+ window layer (< 300 Å), demonstrating large APD gains (G>90) and high sensitivities of 5–3 A/W in blue-ultraviolet optical region under very low reverse bias condition of 33 V.
Materials Design of Ferromagnetic Diamond
Authors: Kenmochi Kazuhide , Sato Kazunori , Yanase Akira , Katayama-Yoshida Hiroshi
Published: July 2005

We propose materials design of ferromagnetic diamond without any transition metal elements based on first principles calculations. The electronic structure and the magnetic properties of impurities-doped diamond are calculated by using the Korringa-Kohn-Rostoker method within the local spin density approximation with taking into account disorder using coherent potential approximation. It is found that H atoms which are doped into tetrahedral interstitial sites show finite local magnetic moments. Moreover, the impurities-doped diamond show ferromagnetism with half-metallic density of states.
Preparation of Atomically Smooth TiO2 Single Crystal Surfaces and Their Photochemical Property
Authors: Yamamoto Yuichi , Nakajima Kazuko , Ohsawa Takeo , Matsumoto Yuji , Koinuma Hideomi
Published: July 2005

Atomically smooth rutile TiO2(110), (100), (001), (111) and (101) surfaces were obtained for the first time by an appropriate cleaning and subsequent thermal treatment of commercially available single crystals. The annealing temperature for obtaining the ultra-smooth surface varied between 400 and 900°C depending on the crystallographic planes. The key point to the successful preparation of the regularly stepped TiO2 surface was an HF treatment for the removal of surface impurities. By using these well-defined TiO2 surfaces, the photochemical property was found to depend on the surface orientation; the photo-reduction of Ag+ to Ag metal from an aqueous solution proceeded in the order of (101) > (100) > (001) > (111) > (110) on the TiO2 surfaces.
Charge Neutralization Using Focused 500 eV Electron Beam in Focused Ion Beam System
Authors: Komoda Hirotaka , Yoshida Masaaki , Yamamoto Yoh , Iwasaki Kouji , Watanabe Heiji , Yasutake Kiyoshi
Published: July 2005

We have proposed a technique for novel charge neutralization in a focused ion beam (FIB) system. To neutralize positive charges induced by FIB, this technique utilizes a focused 500 eV electron beam instead of an electron shower that often causes negative charges in a broad area around the FIB-irradiated point. We used erasable-programmable read-only memory devices to monitor surface charges. The results showed that the focused electron beam is effective for charge neutralization and prevented threshold voltage shifts of both irradiated and neighboring transistors. We also found that the ratio of electron to ion beam currents is a key parameter to achieving effective charge neutralization.
InGaAs/InP Quantum Dots Induced by Self-Organized InAs Stressor-Islands
Authors: Riikonen Juha , Sormunen Jaakko , Mattila Marco , Sopanen Markku , Lipsanen Harri
Published: July 2005

A material system utilizing InGaAs/InP quantum wells (QWs) and InAs islands to create strain-induced quantum dots (SIQDs) is introduced. The SIQDs are fabricated in situ by growing self-organized stressor-islands on top of a near-surface QW. The confinement of carriers in the SIQDs is studied by photoluminescence. Emission peak from the SIQD ground state transition is redshifted by 64 meV from the quantum well peak. Low-temperature luminescence from the SIQD is observed around 0.8 eV (1.55 µm). Altogether, four SIQD states are identified having a level splitting of 15 meV.
Fabrication of Fully Epitaxial Magnetic Tunnel Junctions Using Full-Heusler Alloy Co2Cr0.6Fe0.4Al Thin Film and MgO Tunnel Barrier
Authors: Marukame Takao , Kasahara Takashi , Matsuda Ken-ichi , Uemura Tetsuya , Yamamoto Masafumi
Published: July 2005

Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated using a Co-based full-Heusler alloy Co2Cr0.6Fe0.4Al (CCFA) thin film and a MgO tunnel barrier. The fabricated MTJs had the following layer structure: MgO buffer layer/CCFA lower electrode/MgO tunnel barrier/CoFe upper electrode, grown on a MgO single-crystal substrate. All layers were successively deposited in an ultrahigh vacuum chamber through the combined use of magnetron sputtering and electron beam evaporation. RHEED patterns observed in situ for each layer during preparation clearly indicated that all layers grew epitaxially with the (001) basal plane. The microfabricated epitaxial CCFA/MgO/CoFe MTJs demonstrated relatively high tunnel magnetoresistance ratios, for MTJs using a full-Heusler alloy, of 42% at room temperature and 74% at 55 K. These results confirm the promise of an epitaxial MTJ using a Co-based full-Heusler alloy as a key device structure utilizing the potentially high spin polarization of this material system.
Resistance Switching of Al/(Pr,Ca)MnO3 Thin Films
Authors: Kim Chang Jung , Chen I-Wei
Published: July 2005

We investigated the current-voltage responses and switching characteristics of (Pr,Ca)MnO3 thin films with various electrodes and interfacial layers. We found the resistance of the electrode-film constructs is dominated by interface resistance, and switching is an interfacial phenomenon with characteristic non-linear current-voltage responses under both static and dynamic conditions. Reactive metal top electrodes such as Al can reliably provide a non-ohmic interface exhibiting resistance switching under single-pulse voltage stimulation.
Attempt at Visualizing Breast Cancer with X-ray Dark Field Imaging
Authors: Ando Masami , Yamasaki Katsuhito , Toyofuku Fukai , Sugiyama Hiroshi , Ohbayashi Chiho , Li Gang , Pan Lin , Jiang Xiaoming , Pattanasiriwisawa Wanwisa , Shimao Daisuke , Hashimoto Eiko , Kimura Tatsuro , Tsuneyoshi Masazumi , Ueno Ei , Tokumori Kenji , Maksimenko Anton , Higashida Yoshiharu , Hirano Masatsugu
Published: July 2005

X-ray dark-field imaging (DFI) can clearly visualize breast cancer phantoms and cancer cell nests, stroma, fat tissue, ductus lactiferi, muscle, collagen fibers at stroma and calcification in a 2.8-mm-thick breast cancer pathological specimen. The system comprises a Bragg asymmetric-cut monochro-collimator and a 2.124-mm-thick Si 440 Laue diffraction analyzer at 35 keV. Both optical elements are Floating Zone made silicon crystals. The view size of 33 mm (H) ×19.5 mm (V) and the spatial resolution of 10 µm or better are obtainable at the vertical wiggler beamline BL14B at the Photon Factory.
Three-Dimensional Imaging of GaN Films Using Transient Two-Photon Absorption Excited by Near-Infrared Laser Pulses
Authors: Abe Yasuhiro , Toda Yasunori , Hoshino Katsuyuki , Arakawa Yasuhiko
Published: July 2005

Two-photon absorption (TPA) imaging, based on a transient pump-probe measurement, has been demonstrated for characterizing the nonlinear optical properties of GaN films in three-dimensions. The use of near-infrared excitation light demonstrated the capability to probe changes in TPA inside the structure, which is closely associated with fluctuations in defect states. The TPA coefficient at 1.55 eV was evaluated to be ∼ 0.12 cm/GW for a standard GaN film. A spatial resolution better than λ/2, for an excitation wavelength of 800 nm, was achieved.
Hard X-ray Diffraction-Limited Nanofocusing with Kirkpatrick-Baez Mirrors
Authors: Mimura Hidekazu , Matsuyama Satoshi , Yumoto Hirokatsu , Hara Hideyuki , Yamamura Kazuya , Sano Yasuhisa , Shibahara Masafumi , Endo Katsuyoshi , Mori Yuzo , Nishino Yoshinori , Tamasaku Kenji , Yabashi Makina , Ishikawa Tetsuya , Yamauchi Kazuto
Published: July 2005

Nanofocused X-ray beams are necessary for nanometer-scale spatial microscopy analysis. X-ray focusing using a Kirkpatrick-Baez setup with two total reflection mirrors is a promising method, allowing highly efficient and energy-tuneable focusing. In this paper, we report the development of ultraprecise mirror optics and the realization of a nanofocused hard-X-ray beam. Fabricated mirrors having a figure accuracy of 2 nm peak to valley height give ideal diffraction-limited focusing at the hard X-ray region. The focal size, defined as the full width at half maximum in the intensity profile, was 36 nm ×48 nm at an X-ray energy of 15 keV.
Protein Cryocrystallography Using Laser-Processed Crystal
Authors: Kitano Hiroshi , Matsumura Hiroyoshi , Adachi Hiroaki , Murakami Satoshi , Takano Kazufumi , Inoue Tsuyoshi , Mori Yusuke , Doi Masaaki , Sasaki Takatomo
Published: July 2005

We propose a new procedure in biological cryocrystallography, using the laser-ablation technique. This is the first report on the successful processing of cryo-cooled crystals to create a “protein crystal ball” that is conducive to X-ray diffraction (XRD) data collection. Pulsed UV laser soft ablation (PULSA) modifies protein crystals into a spherical shape and removes surrounding materials, but does not negatively affect crystallinity and may improve diffraction data quality. Additionally, we demonstrate treatment of problematic samples to make them serviceable for XRD analysis. Isolation of single crystals can be performed after flash cooling with the PULSA technique.
Hydrogen Gas Generation by Splitting Aqueous Water Using n-Type GaN Photoelectrode with Anodic Oxidation
Authors: Fujii Katsushi , Karasawa Takeshi , Ohkawa Kazuhiro
Published: July 2005

Hydrogen gas generation from a counterelectrode was clearly observed for the first time using light-illuminated n-type GaN as a working photoelectrode in an electrolyte. The application of extra bias to a working electrode was required to obtain a sufficient volume of generated gas. The reactions at the GaN photoelectrode were both GaN decomposition and water oxidization, simultaneously.
High-Critical-Current-Density SmBa2Cu3O7-x Films Induced by Surface Nanoparticle
Authors: Yoshida Yutaka , Matsumoto Kaname , Miura Masashi , Ichino Yusuke , Takai Yoshiaki , Ichinose Ataru , Horii Shigeru , Mukaida Masashi
Published: July 2005

In oxide-based superconducting thin films, conceivable factors that give rise to a pinning center include dislocations, precipitates, twin boundaries, and a-axis-oriented phases. In this study, crystalline defects were created perpendicular to a high-J
c Sm1+x
Ba2-x
Cu3O
y
film surface during a film deposition process. We obtained extremely high J
c values, J
c=0.37 MA/cm2 (77 K, B∥c, B=5 T) and J
c=0.1 MA/cm2 (77 K, B∥c, B=8 T). These values are equal to or exceed that of the previously reported NbTi wire material measured in a high magnetic field at 4.2 K.
High Field X-Ray Diffraction Studies on MnFeP0.5As0.5
Authors: Koyama Keiichi , Kanomata Takeshi , Watanabe Kazuo
Published: July 2005

High field X-ray diffraction measurement was performed on a ferromagnetic compound MnFeP0.5As0.5 which is recently found to be a new candidate as magnetic refrigeration materials. The compound with a hexagonal Fe2P-type structure shows a field-induced isostructural phase transformation with a hysteresis by applying a magnetic field, accompanied by the metamagnetic transition from the paramagnetic to the ferromagnetic state at just above the Curie temperature of 284 K. We found that the cell volume slightly and continuously decreases with increasing magnetic fields through the field-induced phase transition, although the lattice parameter ratio c/a drastically changes.
Improvement in Threshold Voltage of 1.55-µm Buried-Heterostructure Vertical-Cavity Surface-Emitting Laser
Authors: Asaka Kota , Ohiso Yoshitaka , Okamoto Hiroshi , Iga Ryuzo , Kishi Kenji , Tohmori Yuichi
Published: July 2005

We report on 1.55-µm vertical-cavity surface-emitting lasers (VCSELs) with a buried heterostructure (BH) fabricated on an undoped GaAs/AlAs distributed Bragg reflector (DBR). These BH VCSELs exhibit a low threshold voltage of 1.3 V due to both our improved p-InP/InGaAsP DBR design and the introduction of an intracavity structure for an n-contact. Our BH VCSEL also shows a single transverse mode with a side-mode suppression ratio of more than 40 dB even at high injection currents under cw operation, and the potential to achieve a maximum modulation bandwidth of 4.7 GHz.
Beam-Shaping Technique for End-Pumping Yb-Doped Fiber Laser with Two Laser-Diode Arrays
Authors: Ohashi Hiroyuki , Gao Xin , Saito Masayuki , Okamoto Hiroshi , Takasaka Masaomi , Shinoda Kazunori
Published: July 2005

We describe a beam-shaping technique for two air-cooled high-power laser-diode arrays for pumping an Yb-doped double-clad fiber laser. In this technique, two right-angle prisms are employed to reshape the pumping beam. As a result, the beams of two air-cooled high-power laser-diode arrays were effectively coupled to the Yb-doped double-clad fiber, and a single-mode output beam of 23.3 W in the 1,080-nm region was obtained.
Ion Modification for Improvement of Insulating and Ferroelectric Properties of BiFeO3 Thin Films Fabricated by Chemical Solution Deposition
Authors: Uchida Hiroshi , Ueno Risako , Nakaki Hiroshi , Funakubo Hiroshi , Koda Seiichiro
Published: July 2005

Ion modification techniques for improving the insulating and ferroelectric properties of BiFeO3 (BFO) thin films are reported. Rare-earth-substituted BFO films with chemical compositions of Bi1.00-x
RE
x
Fe1.00O3 [RE = La and Nd] were fabricated on (111)Pt/TiO2/SiO2/(100)Si substrates using a chemical solution deposition technique. Well-saturated P-E curves were obtained for La3+- and Nd3+-substituted BFO films, while the curve of a nonsubstituted BFO film was distorted due to the leakage current. Remanent polarization (P
r) values measured at 10 K were respectively 44 and 51 µC/cm2, for La3+- and Nd3+-substituted BFO films, which are significantly superior to conventional Pb-free ferroelectrics.
Scanning Tunneling Microscope (STM)-Excited Molecular Fluorescence from Porphyrin Thin Films
Authors: Liu Hongwen , Nishitani Ryusuke , Ie Yutaka , Yoshinobu Tatsuo , Aso Yoshio , Iwasaki Hiroshi
Published: July 2005

Scanning tunneling microscope (STM)-excited molecular fluorescence from Meso-tetrakis (3,5-di-tertiarybutyl-phenyl) porphyrin (H2TBPP) thin films with 1–4 nm in thickness on gold (111) and highly oriented pyrolytic graphite (HOPG) surfaces has been respectively investigated in air at room temperature. The thin films of porphyrin were prepared by using spin-casting method. Molecular fluorescence emitted from porphyrin on Au(111) was observed, in company with plasmon-mediated light emission from gold substrate. No light is observed from porphyrin on HOPG. Mechanisms of such different luminescent properties of the STM junctions are discussed.
Spin Polarization Effects on O2 Dissociation from Heme-O2 Adduct
Authors: Tsuda Muneyuki , Diño Wilson Agerico , Kasai Hideaki
Published: July 2005

We consider singlet and triplet iron-porphyrin-O2 (FeP-O2) adducts to investigate spin polarization effects on the FeP-O2 interaction using ab initio calculations based on density functional theory (DFT). The presence of the imidazole (Im) ligand induces spin polarization from O2 to Fe in the triplet (Im)FeP-O2 adduct. The O-O bond of the triplet (Im)FeP-O2 is weaker than that of the triplet FeP-O2 because of this spin polarization effects. Our results suggest that magnetization of heme or heme-based nanomaterials may be utilized as cathode electrode catalysts in polymer electrolyte fuel cells (PEFCs).